2026-02 Security update (KB5077181) (26200.7840) installation completed and continue to update and then 0x800f0991

Question

2026-02 Security update (KB5077181) (26200.7840) installation completed and continue to update and then 0x800f0991

JDB 115

High,

I installed Win11 pro last saturday 07/2/2026 - new laptop HP Elitebook 8 AD3T0ET#UUG

Yesterday update 2026-02 installed without problems (installation completed) ... (sorry messages are in, Dutch)

Today same update is still coming(and continue) in and trying to apply (twice) ... now error 0x00f0991

How can this happens ... and now ?

2026-02 Beveiligingsupdate (KB5077181) (26200.7840) (2)

De installatie is mislukt op ‎11/‎02/‎2026 - 0x800f0991 (failure)

2026-02 Beveiligingsupdate (KB5077181) (26200.7840)

De installatie is voltooid op ‎10/‎02/‎2026 (= installation completed)

JDB 115 Reputation points

2026-02-11T16:18:10.9066667+00:00

Microsoft Windows 11 Pro

Build 26200.7623
Luboš Motl 210 Reputation points

2026-02-11T18:17:32.21+00:00

I have the same error (repeatedly) with the same update, in a Czech Win 11 Home 26200.7623 edition of Windows on an ASUS OLED Vivobook. I first got the same error with 983 at the end (loading and installing was first very slow at many places), tried to repeat it.

The second attempt (simple retry) ended with "finished", no restart required, but the update was restarted seconds later automatically, and ended with this 991 error mentioned above, which I later got several more times. I did sfc /scannow, clean, dism checkhealth, scanhealth, clean, restorehealth without files, didn't help, erasing some files with dism ended with another error. Erasing SoftwareDistribution folder while 2 services turned off did not help. Many of these things were recommended by Copilot and Gemini. Another strange anomaly was that during a reboot, I saw 0-30% installation while turning off, but nothing while turn the PC on again. So the Windows Update history actually says that it was "successfully installed" although it wasn't. Quite clearly, something is partly installed, thinks it is complete but it is not or vice versa. The troubleshooter also says that Windows Update is OK which it's not. I also quickly downloaded MSU for the patch from the Windows Catalog, it ended with This patch is already installed.

I postponed updates for a week, ideally I would want a next cummulative update to fix it directly. If it won't happen, the next plan is (either DISM restorehealth with some ISO file or) the "fix problem using Windows Update" new Windows 11 tool. But I am afraid that the system is trying to defend against something really fatally destructive, and it might be related to some access rights, perhaps in the BIOS (which I updated to the latest version by one notch, after the 991 errors). One CBS persist log file produced had 3 GB which I find crazy, there are several other CBS log files in the 300-600 MB interval each.
Michele Coratti 5 Reputation points

2026-02-11T18:25:56.7133333+00:00

I'm getting same problem on factory new HP ProDesk 4 TWR G1i with latest BIOS from "HP Support Assistant" and Windows 11 Pro 24H2 (build 26100.7705)
JDB 115 Reputation points

2026-02-11T18:37:40.6133333+00:00

I completed all the 5 steps of the Q&A assist .... + rebout + retry the update ... reaching 100% of the installation .... and then ... same error code 0x800f0991 ....

I will wait some days for other suggestions .... if no solution I will reinstall Win 11 PRO
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Luboš Motl 210 Reputation points

2026-02-11T18:44:11.2866667+00:00

Johan, just don't do that, it will fix absolutely nothing. I have the same error 991 on the same *181 February patch, my Windows was reinstalled last Monday after some bizarre blocking of access to OneDrive (and Copilot's destructive recommendation to run various ICACLS commands setting access rights that destroyed my ability to login anywhere). It is also a rather new notebook, ASUS OLED Vivobook bought in September. I believe these errors are purely due to some glitch on Microsoft's side, probably some wrong cooperation with the BIOS of our machines or something like that, and if you reinstall Windows, you will be back to the exact same state where you are now. If the thing works for you otherwise, don't reinstall it, you won't be able to install the patch even after new install of Win 10, that is my strong belief. Instead, pause Windows Update for a week or two, hope that MS will release another update, perhaps 2nd Tuesday of March when the cumulative update will include this problematic February one plus something new. I am surely annoyed by this deep imperfection as much as you are but I have already learned that in similar situations, tough cures to solve things create more problems than they solve.
Luboš Motl 210 Reputation points

2026-02-11T19:20:58.9966667+00:00

Johan, I have the same 991 error, tried pretty much the same things. I think that reinstalling Windows won't help you, it will bring you to the exact same situation because you have done nothing wrong, Microsoft and/or HP (and ASUS) and companies did something, and it isn't fixed yet.

But if you are so radical, have you tried something that I am also somewhat afraid of although it is far less destructive than a Windows reinstall? Windows 11 has this new tool "fix problems using Windows Update". It should download all required files and settings from the Windows Update server to bring your PC to the level of Windows that is officially indicated. In Windows, go to Settings, System, Recovery, and in the 2nd row you see the translation of "fix problems using Windows Update", with the "reinstall now" button. It should work almost just like Windows Update, but reinstall all files that are expected from the current version. Once you click at Reinstall now, you will be given a blue dialog where you can check "automatic restart after install complete" if you wish.

This process may take some (two?) hours because it will install all files for your version and the process doesn't have to be too optimized. The conclusion may be that it will suddenly work. But I think it is more likely that in one moment or another, it will complain about a similar error; or it will decide that your Windows don't need that fix (although they do need it); or it may end up in a worse thing because this 991 error is actually a sign of our computers' defense against something that would be devastating for them.

Nine days ago I was "fixing" a problem with access to OneDrive subfolders and Copilot (AI) told me it was perfectly safe to run various ICACLS commands to change ownership or access rights of tens of thousands of files everwhere, I knew I was in trouble when I saw it was working for such a long time etc. Of course my user profiles became totally unusable, impossible to create new ones, I really did need a clean cloud reinstall of Windows. Now, I only have trouble to install one particular update, everything else works so great. With the experience, I will probably try to keep this state even up to the autumn for the possible 26H2.

Jose Antonio Hernandez Martinez 0

I'm getting the same error, initially I was able to install the update but now it appears again failing continuously:

User's image

Reviewing the logs I see this:

Installation Failure: Windows failed to install the following update with error 0x800F0991: 2026-02 Security Update (KB5077181) (26200.7840).

and in the CBS.log


2026-02-11 21:50:51, Warning               CBS    Exec: Failed to pre-stage package: Microsoft-Windows-VBSCRIPT-WOW64-Package~31bf3856ad364e35~wow64~es-ES~10.0.26100.1, component identity: amd64_microsoft-windows-o..documents.resources_31bf3856ad364e35_10.0.26100.4484_it-it_3ae690d4a53f5934, file: oobe_learn_more_activity_history.htm, sandbox: \\?\C:\Windows\SoftwareDistribution\Download\4c549d926ae3a8d7e16f54ab722e0852\metadata\Windows11.0-KB5077181-x64\, file format: 0 [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE]

2026-02-11 21:50:54, Info                  CBS    Exec: Processing complete.  Session: 31234967_3290011272, Package: Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.7840.1.19, Identifier: KB5077181 [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE]
2026-02-11 21:50:54, Error                 CBS    Failed to perform operation.  [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE]

I expect some help from more than a bot...

kevin kh 10 Reputation points

2026-02-12T13:29:14.56+00:00

I faced the same issue once. Impossible to install KB5077181 ( 26200.7840) like the

KB5074109 build 26100.7623, I tried via repairing Windows update files, it's called "Fix problems with windows update". It will reinstall core windows OS but your data and settings aren't touched. Try it out.it takes time the process is very long even with my high end pc , but be patient until the very last % and many restart.

I found this process by Gemini and I'm so grateful because I tried since the patch KB5074109 build 26100.7623 so many manipulations and always the same code error. Very frustrating but you will get there
Luboš Motl 210 Reputation points

2026-02-12T13:55:24.28+00:00

Kevin, I was told about it by Gemini and Copilot, too. So the new tool Fix problems using Windows Update has worked for you in the previous late January preview patch? Are you sure you had the 991 or 983 errors before that?
kevin kh 10 Reputation points

2026-02-12T14:25:20.6266667+00:00

Actually the KB5074109 build 26100.7623 wouldn't install but when I heard all the troubleshooting he brought specially when NVIDIA ask to remove this update ( I think in my mind that finally it was a good news), I blocked the update on windows update until February 10th and Gemini said it was the best move to do because I knew they will release a better update more stable etc .. and like it was predicted windows update skip the KB5074109 build 26100.7623 for the KB5077181 ( 26200.7840) and I install it with 5 others updates, the update keep blocking during the installation always with the same code error ( I was so frustrated and tired of this situation anyway, then I used the fix problem window update with Gemini on my phone to guide me guide step by step and it works ( before we even tried to install directly the update but didn't work , I really tried everything except the iso solution)... And for both it was the EXCATLY the same error. It download at 100% and when the installation occurs around 70% it failed I had the code error 0x800F0991 always not other code error.

Sorry for my bad English I'm french so I hope you get what I say
JDB 115 Reputation points

2026-02-14T13:48:49.6133333+00:00

Yesterday evening I decided to use : SYTSTEM - RECOVERY - FIX PROBLEMS USING WINDOWS UPDATE

After about 2 hours - reboot - and problems are gone ! No lost data (I use also Onedrive - Icloud en Proton Cloud) - All Apps, Office, application still works fine.

Instllation is now (HP Elitebook 255H - 32 GB RAM)

Edition Windows 11 Pro

Version 25H2

Installed on ‎13/‎02/‎2026

OS build 26200.7840
kevin kh 10 Reputation points

2026-02-14T13:52:03.91+00:00

The same
Luboš Motl 210 Reputation points

2026-02-15T09:29:36.7033333+00:00

Dear Gentlemen, I have joined your Successful Team. Did Settings, System (in the left sidebar), Recovery (in the right column), Fix Problems Using Windows Update (2nd in the right column). Did not check Automatic Restart. It switched to Windows Update except that the new patch was called a "Win 11 25H2 (repair edition)" (in Czech, whatever it is in your language).

The Windows Update screen spent 10 minutes downloading, 55 minutes installing while I could work, the percentages were much more regular than I saw in a month, and then I got the restart request which Windows Update failed to give me 20 times in the recent week. ;-) The restart only took 5 minutes in the "installation on black screen", plus the first login was about 2 minutes slower than I expected. Several restarts on the black screens, counting up to 100% maybe twice, slightly smaller fonts than the usual installation of the patches. The new tool seems to be working, I am on 7840 now, too.
kevin kh 10 Reputation points

2026-02-16T17:02:29.5333333+00:00

Me I had the same error code for the KB5074109 build 26100.7623 but when I heard I wasn't alone and I asked to Gemini if the update was a bad one it said yes and it was better to put windows update in pause until the 10 February (3 weeks)

The 11 February I re opened windows update and fortunately the KB5074109 build 26100.7623 was gone and I had the KB5077181 ( 26200.7840) and many others small updates , all of them works fine expect the KB5077181 the same issues , the download was full and during the installation around 70% it failed with again the same error. So Gemini ask to go somewhere in the settings to clean and looking for troubleshooting on windows update, so it works after many restart pc and I did few command lines on cmd and finally it worked since windows update works perfectly. But if all this process didn't work that day I was ready to try the iso windows 11 steps.

Try Gemini it's free and very convenient I use it on my phone . Good luck you will find a way and go to facultatives updates, it's what I've done too.
Luboš Motl 210 Reputation points

2026-02-16T17:14:07.44+00:00

I have talked to Gemini for hundreds of hours about a thousand of topics, including a massive thread on this update, various functions in Windows. Gemini and other AI may persuasively and grammatically correctly argue in favor of many things, it tends to be a Yes-man who rationalizes what you write and emulates your style. Sometimes Gemini, albeit the best large language model on the market, also hallucinates, and offers wrong answers. They tend to be wrong especially when some "complicated analog" information is involved. It can easily say that a town is in the opposite direction than it is, confuse it with another town that is comparably large and comparably far from a nearby city, and so on. But in these threads about the error, I found out that quite often, Gemini (and others) pays a low attention to details in complicated boring data, exactly what you expect conventional computers to be very good at. In this way, the AI is "more human" than humans. So on a Wikipedia page on Windows 11 versions, I easily found out the versions and which patches produced them, which versions were preview, and so many other things. Gemini seemed to be disinterested in distinguishing numbers 7623 from 7705 and 7740 etc. although this information was clearly crucial to properly discuss my glitch.

So Gemini and Copilot also recommended the reinstall using DISM with an ISO source - which by the way does NOT work, as some users reported on this server. It recommended other things that didn't work, and Copilot previously told me to write "perfectly safe" commands ICACLS to mass change access rights to all files on my hard disk (as a cure for an access to OneDrive subfolders) which made my PC unusable and I had to reinstall it. So you just can't believe everything. Gemini is extremely useful but literally everything may be wrong or a hallucination designed to sound perfectly plausible - but still an easily disprovable lie. The 991 error may appear with various patches and it is surely independent of the previous level of Windows. On this Vivobook, I got the 991 error with the 7840 patch through KB5077181 (originally the error was 983), but when I was in the 991 error mode, I also got 991 from the attempted late January preview patch that should lift Windows to 7705. The precise reason is unknown. Something recently appeared in these patches that seems incompatible with something in Windows 11 computers, especially very new computers, and the only known cure (except for a clean reinstall) is the new tool Fix Problems using Windows Update - even ISO DISM installs fail.
AndrewM 0 Reputation points

2026-02-16T19:20:47.6633333+00:00

I am having the same issue. KB5077181 will not install and gives error 0x800f0991. I spent the whole day with ChatGPT trying to solve it. I finally did a manual install and even that failed. ChatGPT said that I could either do an ISO recovery, or wait until the next CU. A quick conversation with CoPilot this morning revealed that this is affecting a lot of users. CoPilot also agreed with ChatGPT about the remaining options. It suggested to wait for now.
Luboš Motl 210 Reputation points

2026-02-16T19:55:53.0166667+00:00

Andrew, what did you mean by the manual install? Copilot often advises DISM with ISO etc. But I follow about 5 pages on this server and the only cure for the 991 error is Settings, System, Recovery, Fix Problems with Windows Update (second among the tools in the right sidebar list), click at "reinstall now". The number of people who have fixed the 983 and 991 errors of Windows Update by this new tool of Windows 11 is at least 6 by now. Johan, Kevin, me, Brian, several more... Brian still says wrong things about why the problem occurred and what was why it was fixed, but he still fixed his Windows system.

Again, this tool is new, did not exist before Windows 11, and is far more successful and systematic than any usage of the DISM or similar command. It preserves your personal data, settings, apps. After the reinstall, my index doubled in size so I restarted the indexing to get back from 9 GB to 5 GB windows.edb, but this is a tiny imperfection relatively to the possibly deep inconsistency in our WinSxS that leads to the 991 error.

991 means that the OS thinks that some files are already OK, doesn't download them but it doesn't actually physically own them. You need to run the deeper reinstall-like Windows Update process which looks like Windows Update patch on the surface but actually does all the steps of Windows installation over your system, including the seemingly unnecessary ones, and in 1-2 hours, it just restarts in the newest 7840 version. This tool is experimentally far more successful than any work with the ISO file, except for a clean reinstall, and it's possible that even a clean reinstall of Windows - erasing personal data - would repeat the 991 error if you tried to update it to the latest version. The Fix Problems with Windows Update brings you to the latest level of Windows automatically, just like the normal Windows Update to the newest patch.
AndrewM 0 Reputation points

2026-02-16T20:18:47.8933333+00:00

By "manual" install, I mean downloading the msu file from Microsoft and installing it as described here: https://share.google/aimode/nN0HpIJqX0Q8chV1h

It did not work. Went to 100% then failed.
AndrewM 0 Reputation points

2026-02-16T20:21:32.3133333+00:00

Given the number of people who are reporting reboot (and other) problems once they do get KB5077181 installed, my failure to install it may be a blessing in disguise for now...
AndrewM 0 Reputation points

2026-02-17T02:50:13.69+00:00

Here is direct quote from CoPilot about KB5077181...

“Based on current reporting and widespread user feedback, KB5077181 appears to be one of the most problematic Windows 11 cumulative updates released in quite some time.”
Luboš Motl 210 Reputation points

2026-02-17T02:57:47.15+00:00

Andrew, my latest 7840 works flawlessly after the error was circumvented, and I think it is true for everybody here who had the error, and almost everybody who installed it. You Copilot thread is wrong, your desire not to fix the error using a tool that is now amazingly tested is rather crazy, and given the cumulative character of the updates, it is more likely than not that you will be unable to update your Windows at least up to 26H2 in the autumn.
AndrewM 0 Reputation points

2026-02-17T03:34:26.12+00:00

I am very happy that your system works, but I don't think you can say the Copilot thread is wrong. It simply advised me that if my system is stable (which it is) then I might be better off waiting for a patch to be released. Seemed like sound advice to me given the complaints about system lock outs, infinite boot loops, etc. that are experienced by a growing number of users who do get it installed. I might try your solution if there is no patch or hotfix released in a few weeks. Thank you for the advice.
Luboš Motl 210 Reputation points

2026-02-17T04:04:59.0466667+00:00

Andrew, I can show you my own Copilot thread where it totally encouraged me to try all the options, including DISM with ISO, and the last portion was (a rarely correct) persuasion that I should try Fix Problems With Windows Update. Two weeks ago, it also convinced me to run ICACLS commands on my whole file system that totally wrecked my Windows. Much of the AI conversation is just echoing your own opinions in a more polished, complete prose! It is just completely wrong to treat some opinions on difficult questions shared by AI as some authoritative truth.
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Teagan Roehl 0 Reputation points

2026-02-19T04:15:25.7866667+00:00

(KB5077181) (26200.7840) 0x80070306 I'm getting a slightly different error
i have run the following command prompts and it still fails.

DISM.exe /Online /Cleanup-Image /RestoreHealth

sfc /scannow
net stop bits

net stop wuauserv

net stop msiserver

net stop cryptsvc

Ren %Systemroot%\SoftwareDistribution SoftwareDistribution.old

Ren %Systemroot%\System32\catroot2 catroot2.old

net start bits

net start wuauserv

net start msiserver

net start cryptsvc
Philippe Degand-Saint 0 Reputation points

2026-02-20T17:48:48.78+00:00

Same problem not resolved by Microsoft
AndrewM 0 Reputation points

2026-02-23T03:30:45.99+00:00

So today, after two weeks of almost daily checks telling me to wait, CoPilot finally advised me to try the Fix Problems With Windows Update solution that Lubos advised earlier to fix Error 0x800f0991. My reluctance was eased when it told me that the Windows Boot Loop issues were only experienced by people who installed it over corruption caused by previous failed installs and that the Fix Problems With Windows Update would minimize (if not eliminate) that risk. After running the Fix Problems With Windows Update, everything worked fine and Windows Update told me that I was all up to date.
Kim Green 0 Reputation points

2026-02-23T16:50:51.5+00:00

Same problem. I've made sure Windows is healthy and other updates are installed sfc/DISM. Using standalone I got it downloaded but all attempts fail on the install part. No relevant logs helpful.

Windows Update automated diagnostic unable to run.

msdt.exe -id WindowsUpdateDiagnostic (recommended by Microsoft Help) Troubleshooters have moved and this tool will be retired

System -> Troubleshoot -> Other Troubleshooters -> Windows Update went to white screen and stayed there, no help.
AndrewM 0 Reputation points

2026-02-24T22:36:10.4233333+00:00

Try Settings -> System ->Recovery ->Fix Problems with Windows Update -> Reinstall Now

4 answers

Your answer

JDB 115 Reputation points

2026-02-11T16:18:10.9066667+00:00

Microsoft Windows 11 Pro

Build 26200.7623
Luboš Motl 210 Reputation points

2026-02-11T18:17:32.21+00:00

I have the same error (repeatedly) with the same update, in a Czech Win 11 Home 26200.7623 edition of Windows on an ASUS OLED Vivobook. I first got the same error with 983 at the end (loading and installing was first very slow at many places), tried to repeat it.

The second attempt (simple retry) ended with "finished", no restart required, but the update was restarted seconds later automatically, and ended with this 991 error mentioned above, which I later got several more times. I did sfc /scannow, clean, dism checkhealth, scanhealth, clean, restorehealth without files, didn't help, erasing some files with dism ended with another error. Erasing SoftwareDistribution folder while 2 services turned off did not help. Many of these things were recommended by Copilot and Gemini. Another strange anomaly was that during a reboot, I saw 0-30% installation while turning off, but nothing while turn the PC on again. So the Windows Update history actually says that it was "successfully installed" although it wasn't. Quite clearly, something is partly installed, thinks it is complete but it is not or vice versa. The troubleshooter also says that Windows Update is OK which it's not. I also quickly downloaded MSU for the patch from the Windows Catalog, it ended with This patch is already installed.

I postponed updates for a week, ideally I would want a next cummulative update to fix it directly. If it won't happen, the next plan is (either DISM restorehealth with some ISO file or) the "fix problem using Windows Update" new Windows 11 tool. But I am afraid that the system is trying to defend against something really fatally destructive, and it might be related to some access rights, perhaps in the BIOS (which I updated to the latest version by one notch, after the 991 errors). One CBS persist log file produced had 3 GB which I find crazy, there are several other CBS log files in the 300-600 MB interval each.
Michele Coratti 5 Reputation points

2026-02-11T18:25:56.7133333+00:00

I'm getting same problem on factory new HP ProDesk 4 TWR G1i with latest BIOS from "HP Support Assistant" and Windows 11 Pro 24H2 (build 26100.7705)
JDB 115 Reputation points

2026-02-11T18:37:40.6133333+00:00

I completed all the 5 steps of the Q&A assist .... + rebout + retry the update ... reaching 100% of the installation .... and then ... same error code 0x800f0991 ....

I will wait some days for other suggestions .... if no solution I will reinstall Win 11 PRO
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Luboš Motl 210 Reputation points

2026-02-11T18:44:11.2866667+00:00

Johan, just don't do that, it will fix absolutely nothing. I have the same error 991 on the same *181 February patch, my Windows was reinstalled last Monday after some bizarre blocking of access to OneDrive (and Copilot's destructive recommendation to run various ICACLS commands setting access rights that destroyed my ability to login anywhere). It is also a rather new notebook, ASUS OLED Vivobook bought in September. I believe these errors are purely due to some glitch on Microsoft's side, probably some wrong cooperation with the BIOS of our machines or something like that, and if you reinstall Windows, you will be back to the exact same state where you are now. If the thing works for you otherwise, don't reinstall it, you won't be able to install the patch even after new install of Win 10, that is my strong belief. Instead, pause Windows Update for a week or two, hope that MS will release another update, perhaps 2nd Tuesday of March when the cumulative update will include this problematic February one plus something new. I am surely annoyed by this deep imperfection as much as you are but I have already learned that in similar situations, tough cures to solve things create more problems than they solve.
Jose Antonio Hernandez Martinez 0 Reputation points

2026-02-11T21:15:15.6866667+00:00

I'm getting the same error, initially I was able to install the update but now it appears again failing continuously:

Reviewing the logs I see this:

Installation Failure: Windows failed to install the following update with error 0x800F0991: 2026-02 Security Update (KB5077181) (26200.7840).

and in the CBS.log

2026-02-11 21:50:51, Warning CBS Exec: Failed to pre-stage package: Microsoft-Windows-VBSCRIPT-WOW64-Package~31bf3856ad364e35~wow64~es-ES~10.0.26100.1, component identity: amd64_microsoft-windows-o..documents.resources_31bf3856ad364e35_10.0.26100.4484_it-it_3ae690d4a53f5934, file: oobe_learn_more_activity_history.htm, sandbox: \\?\C:\Windows\SoftwareDistribution\Download\4c549d926ae3a8d7e16f54ab722e0852\metadata\Windows11.0-KB5077181-x64\, file format: 0 [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE] 2026-02-11 21:50:54, Info CBS Exec: Processing complete. Session: 31234967_3290011272, Package: Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.7840.1.19, Identifier: KB5077181 [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE] 2026-02-11 21:50:54, Error CBS Failed to perform operation. [HRESULT = 0x800f0991 - PSFX_E_MISSING_PAYLOAD_FILE]

I expect some help from more than a bot...
kevin kh 10 Reputation points

2026-02-12T13:29:14.56+00:00

I faced the same issue once. Impossible to install KB5077181 ( 26200.7840) like the

KB5074109 build 26100.7623, I tried via repairing Windows update files, it's called "Fix problems with windows update". It will reinstall core windows OS but your data and settings aren't touched. Try it out.it takes time the process is very long even with my high end pc , but be patient until the very last % and many restart.

I found this process by Gemini and I'm so grateful because I tried since the patch KB5074109 build 26100.7623 so many manipulations and always the same code error. Very frustrating but you will get there
Luboš Motl 210 Reputation points

2026-02-12T13:55:24.28+00:00

Kevin, I was told about it by Gemini and Copilot, too. So the new tool Fix problems using Windows Update has worked for you in the previous late January preview patch? Are you sure you had the 991 or 983 errors before that?
kevin kh 10 Reputation points

2026-02-12T14:25:20.6266667+00:00

Actually the KB5074109 build 26100.7623 wouldn't install but when I heard all the troubleshooting he brought specially when NVIDIA ask to remove this update ( I think in my mind that finally it was a good news), I blocked the update on windows update until February 10th and Gemini said it was the best move to do because I knew they will release a better update more stable etc .. and like it was predicted windows update skip the KB5074109 build 26100.7623 for the KB5077181 ( 26200.7840) and I install it with 5 others updates, the update keep blocking during the installation always with the same code error ( I was so frustrated and tired of this situation anyway, then I used the fix problem window update with Gemini on my phone to guide me guide step by step and it works ( before we even tried to install directly the update but didn't work , I really tried everything except the iso solution)... And for both it was the EXCATLY the same error. It download at 100% and when the installation occurs around 70% it failed I had the code error 0x800F0991 always not other code error.

Sorry for my bad English I'm french so I hope you get what I say
JDB 115 Reputation points

2026-02-14T13:48:49.6133333+00:00

Yesterday evening I decided to use : SYTSTEM - RECOVERY - FIX PROBLEMS USING WINDOWS UPDATE

After about 2 hours - reboot - and problems are gone ! No lost data (I use also Onedrive - Icloud en Proton Cloud) - All Apps, Office, application still works fine.

Instllation is now (HP Elitebook 255H - 32 GB RAM)

Edition Windows 11 Pro

Version 25H2

Installed on ‎13/‎02/‎2026

OS build 26200.7840
kevin kh 10 Reputation points

2026-02-14T13:52:03.91+00:00

The same
Luboš Motl 210 Reputation points

2026-02-15T09:29:36.7033333+00:00

Dear Gentlemen, I have joined your Successful Team. Did Settings, System (in the left sidebar), Recovery (in the right column), Fix Problems Using Windows Update (2nd in the right column). Did not check Automatic Restart. It switched to Windows Update except that the new patch was called a "Win 11 25H2 (repair edition)" (in Czech, whatever it is in your language).

The Windows Update screen spent 10 minutes downloading, 55 minutes installing while I could work, the percentages were much more regular than I saw in a month, and then I got the restart request which Windows Update failed to give me 20 times in the recent week. ;-) The restart only took 5 minutes in the "installation on black screen", plus the first login was about 2 minutes slower than I expected. Several restarts on the black screens, counting up to 100% maybe twice, slightly smaller fonts than the usual installation of the patches. The new tool seems to be working, I am on 7840 now, too.
kevin kh 10 Reputation points

2026-02-16T17:02:29.5333333+00:00

Me I had the same error code for the KB5074109 build 26100.7623 but when I heard I wasn't alone and I asked to Gemini if the update was a bad one it said yes and it was better to put windows update in pause until the 10 February (3 weeks)

The 11 February I re opened windows update and fortunately the KB5074109 build 26100.7623 was gone and I had the KB5077181 ( 26200.7840) and many others small updates , all of them works fine expect the KB5077181 the same issues , the download was full and during the installation around 70% it failed with again the same error. So Gemini ask to go somewhere in the settings to clean and looking for troubleshooting on windows update, so it works after many restart pc and I did few command lines on cmd and finally it worked since windows update works perfectly. But if all this process didn't work that day I was ready to try the iso windows 11 steps.

Try Gemini it's free and very convenient I use it on my phone . Good luck you will find a way and go to facultatives updates, it's what I've done too.
AndrewM 0 Reputation points

2026-02-16T19:20:47.6633333+00:00

I am having the same issue. KB5077181 will not install and gives error 0x800f0991. I spent the whole day with ChatGPT trying to solve it. I finally did a manual install and even that failed. ChatGPT said that I could either do an ISO recovery, or wait until the next CU. A quick conversation with CoPilot this morning revealed that this is affecting a lot of users. CoPilot also agreed with ChatGPT about the remaining options. It suggested to wait for now.
Luboš Motl 210 Reputation points

2026-02-16T19:55:53.0166667+00:00

Andrew, what did you mean by the manual install? Copilot often advises DISM with ISO etc. But I follow about 5 pages on this server and the only cure for the 991 error is Settings, System, Recovery, Fix Problems with Windows Update (second among the tools in the right sidebar list), click at "reinstall now". The number of people who have fixed the 983 and 991 errors of Windows Update by this new tool of Windows 11 is at least 6 by now. Johan, Kevin, me, Brian, several more... Brian still says wrong things about why the problem occurred and what was why it was fixed, but he still fixed his Windows system.

Again, this tool is new, did not exist before Windows 11, and is far more successful and systematic than any usage of the DISM or similar command. It preserves your personal data, settings, apps. After the reinstall, my index doubled in size so I restarted the indexing to get back from 9 GB to 5 GB windows.edb, but this is a tiny imperfection relatively to the possibly deep inconsistency in our WinSxS that leads to the 991 error.

991 means that the OS thinks that some files are already OK, doesn't download them but it doesn't actually physically own them. You need to run the deeper reinstall-like Windows Update process which looks like Windows Update patch on the surface but actually does all the steps of Windows installation over your system, including the seemingly unnecessary ones, and in 1-2 hours, it just restarts in the newest 7840 version. This tool is experimentally far more successful than any work with the ISO file, except for a clean reinstall, and it's possible that even a clean reinstall of Windows - erasing personal data - would repeat the 991 error if you tried to update it to the latest version. The Fix Problems with Windows Update brings you to the latest level of Windows automatically, just like the normal Windows Update to the newest patch.
AndrewM 0 Reputation points

2026-02-16T20:18:47.8933333+00:00

By "manual" install, I mean downloading the msu file from Microsoft and installing it as described here: https://share.google/aimode/nN0HpIJqX0Q8chV1h

It did not work. Went to 100% then failed.
AndrewM 0 Reputation points

2026-02-16T20:21:32.3133333+00:00

Given the number of people who are reporting reboot (and other) problems once they do get KB5077181 installed, my failure to install it may be a blessing in disguise for now...
AndrewM 0 Reputation points

2026-02-17T02:50:13.69+00:00

Here is direct quote from CoPilot about KB5077181...

“Based on current reporting and widespread user feedback, KB5077181 appears to be one of the most problematic Windows 11 cumulative updates released in quite some time.”
Luboš Motl 210 Reputation points

2026-02-17T02:57:47.15+00:00

Andrew, my latest 7840 works flawlessly after the error was circumvented, and I think it is true for everybody here who had the error, and almost everybody who installed it. You Copilot thread is wrong, your desire not to fix the error using a tool that is now amazingly tested is rather crazy, and given the cumulative character of the updates, it is more likely than not that you will be unable to update your Windows at least up to 26H2 in the autumn.
AndrewM 0 Reputation points

2026-02-17T03:34:26.12+00:00

I am very happy that your system works, but I don't think you can say the Copilot thread is wrong. It simply advised me that if my system is stable (which it is) then I might be better off waiting for a patch to be released. Seemed like sound advice to me given the complaints about system lock outs, infinite boot loops, etc. that are experienced by a growing number of users who do get it installed. I might try your solution if there is no patch or hotfix released in a few weeks. Thank you for the advice.
Luboš Motl 210 Reputation points

2026-02-17T04:04:59.0466667+00:00

Andrew, I can show you my own Copilot thread where it totally encouraged me to try all the options, including DISM with ISO, and the last portion was (a rarely correct) persuasion that I should try Fix Problems With Windows Update. Two weeks ago, it also convinced me to run ICACLS commands on my whole file system that totally wrecked my Windows. Much of the AI conversation is just echoing your own opinions in a more polished, complete prose! It is just completely wrong to treat some opinions on difficult questions shared by AI as some authoritative truth.
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Teagan Roehl 0 Reputation points

2026-02-19T04:15:25.7866667+00:00

(KB5077181) (26200.7840) 0x80070306 I'm getting a slightly different error
i have run the following command prompts and it still fails.

DISM.exe /Online /Cleanup-Image /RestoreHealth

sfc /scannow
net stop bits

net stop wuauserv

net stop msiserver

net stop cryptsvc

Ren %Systemroot%\SoftwareDistribution SoftwareDistribution.old

Ren %Systemroot%\System32\catroot2 catroot2.old

net start bits

net start wuauserv

net start msiserver

net start cryptsvc
Philippe Degand-Saint 0 Reputation points

2026-02-20T17:48:48.78+00:00

Same problem not resolved by Microsoft
AndrewM 0 Reputation points

2026-02-23T03:30:45.99+00:00

So today, after two weeks of almost daily checks telling me to wait, CoPilot finally advised me to try the Fix Problems With Windows Update solution that Lubos advised earlier to fix Error 0x800f0991. My reluctance was eased when it told me that the Windows Boot Loop issues were only experienced by people who installed it over corruption caused by previous failed installs and that the Fix Problems With Windows Update would minimize (if not eliminate) that risk. After running the Fix Problems With Windows Update, everything worked fine and Windows Update told me that I was all up to date.
Kim Green 0 Reputation points

2026-02-23T16:50:51.5+00:00

Same problem. I've made sure Windows is healthy and other updates are installed sfc/DISM. Using standalone I got it downloaded but all attempts fail on the install part. No relevant logs helpful.

Windows Update automated diagnostic unable to run.

msdt.exe -id WindowsUpdateDiagnostic (recommended by Microsoft Help) Troubleshooters have moved and this tool will be retired

System -> Troubleshoot -> Other Troubleshooters -> Windows Update went to white screen and stayed there, no help.
AndrewM 0 Reputation points

2026-02-24T22:36:10.4233333+00:00

Try Settings -> System ->Recovery ->Fix Problems with Windows Update -> Reinstall Now

Answer 1

Hi John,

Please try a repair install as the next step. It keeps everything, including apps and files, and reinstalls Windows.

Repair Install Windows 11 using an ISO file

https://www.yourwindowsguide.com/2021/08/repair-install-windows-11-using-an-iso-file.html

Download Windows 11 ISO file from the following link:

https://www.microsoft.com/software-download/Windows11

Under Download ISO file, select Windows 11.
Click Download and choose the Language in which Windows is installed.
Click 64-bit Download to start the download.
When downloaded, open the ISO file, and run Setup.exe to start the upgrade.

Answer 2

Sumit D - IA 161K Independent Advisor

Hi,

It might be a common glitch.

Press Windows+R keys on the keyboard, or Right-click Start on the Taskbar and choose Run.

Type winver.exe

Press Enter.

Could you please post the Build number?

You can also try installing manually:

https://catalog.sf.dl.delivery.mp.microsoft.com/filestreamingservice/files/d8b7f92b-bd35-4b4c-96e5-46ce984b31e0/public/windows11.0-kb5043080-x64_953449672073f8fb99badb4cc6d5d7849b9c83e8.msu

I’m eager to hear back and work together to find a solution.

Luboš Motl 210 Reputation points

2026-02-11T18:38:32.3433333+00:00

Dear Sumit, I have the same 991 error with the same February monthly patch, some details of what I tried and what happened are described in my comment under the original question at the top. The attempted fixes - which universally failed so far - included the MSU file from the Microsoft Catalog server (it downloaded real quickly!). When I ran the MSU, it took some dozens of seconds and then it ended with "This patch is already installed". I would surely bet that all others with the 991 error will see the same "false correct" ending of the MSU attempt, too.

However, the patch is still being offered, and always ends with the 991 error, despite various efforts to clean the WU cache, sfc scannow, restorehealth, deletion of SoftwareDistribution, and some other attempts.

Answer 3

The error code 0x800f0991 typically indicates that there is a problem with the Windows Update components or that a required update is missing. Since you mentioned that the installation of the February 2026 security update (KB5077181) completed successfully but then continued to prompt for installation, it suggests that there may be a conflict or an issue with the update process.

Here are some steps you can take to troubleshoot this issue:

Run the Windows Update Troubleshooter: This built-in tool can help identify and fix problems with Windows Update.
- Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update.
Check for Pending Updates: Sometimes, other updates may be pending that need to be installed before the problematic update can be applied. Check for any other updates and install them.
Reset Windows Update Components: You can reset the Windows Update components manually. This involves stopping the Windows Update service, deleting temporary files, and restarting the service. Instructions for this can be found in Microsoft's support documentation.
Use the DISM and SFC Tools: These tools can repair corrupted system files that may be causing issues with updates.
- Open Command Prompt as an administrator and run the following commands:
  - DISM /Online /Cleanup-Image /RestoreHealth
  - sfc /scannow
Check the Windows Update History: You can review the update history to see if there are any other related errors or issues that might provide more insight.

If the issue persists after trying these steps, consider reaching out to Microsoft Support for further assistance.

References:

Answer 4

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2026-02 Security update (KB5077181) (26200.7840) installation completed and continue to update and then 0x800f0991

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