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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(105.60000000000001, 56.00000000000001%, 20%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EMN%3C/text%3E%3C/svg%3E)
I can't install a Windows 11 update.2026-03 Update (KB5085516) (26200.8039) Install error - 0x800f0991 Install attempt failed twice.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(76.8, 33%, 17%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EDG%3C/text%3E%3C/svg%3E)
Hello, même problème depuis le 23/03.
Antivirus Norton et Windows 11 famille version 25H2 OS build 26200.7171.
merci d’avance pour votre retour
Answer accepted by question author
Hi. I'm David, and I'm happy to help you.
Please clarify the following:
Do you have a third-party antivirus installed? If yes, which one?
Also. What is the current "OS Build" of your Windows 11?
winver, and click OK.If you prefer, share a screenshot. Use the shortcut "Windows + Shift + S" to use the screenshot tool.
Be sure to censor your email address if it appears. The Microsoft Q&A is public.
Looking forward to your reply.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(89.60000000000001, 43%, 18%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EO%3C/text%3E%3C/svg%3E)
I also have the same error.
When I try to reboot, I also can't boot properly, and then have to do a system restore to the last update.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(265.6, 59%, 35%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EMS%3C/text%3E%3C/svg%3E)
I have exactly the same problem. I got a microsoft surface laptop 7th edition.
David,
I'm not sure if I answered correctly the first try.
Screenshot 2026-03-23 133932.png
No third party antivirus.
Michael
AI answer was to reinstall Windows 11 ISO. I downloaded the installer and when run was told I'm running the latest version of Windows 11.