Updates to Windows 11 not installing

Question

Updates to Windows 11 not installing

Peter Wade 20

I have Windows 11 Pro Version 24H2 OS Build 26100.6584. The update to 25H2 will not install despite trying several solutions. It reports error 0x800f0991.

Any help much appreciated.

Peter

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Answer accepted by question author

DaveM121 929K Independent Advisor

The most successful method to install version 25H2 is to use the Windows 11 ISO.

You will need at least 40GB of free space on your C drive for the update (this space will be cleared later automatically).

Please ensure you download the ISO in the same language as you use for the Windows UI, follow the steps, this is then not like re-installing Windows, it is just like an update and your personal files, settings and installed software will not be affected.

Click this link:

https://www.microsoft.com/software-download/windows11

to download the Windows 11 ISO

When the ISO file completes downloading

Disconnect from the Internet

Disconnect all external devices with the exception of a mouse or keyboard.

Temporarily disable any 3rd party Anti-virus you may have installed

Then, in Windows File Explorer, double click the ISO and then run Setup.exe and select the Install option.

Very Important - ensure you select the option to keep your files and apps.

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1 additional answer

Your answer

Answer 1

Error 0x800f0991 typically indicates that there is a problem with the Windows Update components or that required files for the update are missing. Here are some steps you can take to troubleshoot and resolve this issue:

Run Windows Update Troubleshooter: Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters and select Windows Update. Run the troubleshooter and follow the prompts.
Check for Missing Updates: Ensure that all previous updates have been installed. Sometimes, missing updates can prevent the installation of newer versions. Go to Settings > Windows Update and click on Check for updates.
Repair Windows Update Components: You can manually reset the Windows Update components using the Command Prompt. Open Command Prompt as an administrator and run the following commands one by one:
```
   net stop wuauserv
   net stop cryptSvc
   net stop bits
   net stop msiserver
   net start wuauserv
   net start cryptSvc
   net start bits
   net start msiserver
```
Use the System File Checker: Run the System File Checker tool to repair missing or corrupted system files. Open Command Prompt as an administrator and type:
```
   sfc /scannow
```
Wait for the scan to complete and follow any instructions provided.
Check Disk for Errors: Run a disk check to ensure there are no issues with your hard drive. Open Command Prompt as an administrator and type:
```
   chkdsk /f
```
You may need to restart your computer for the check to occur.
Manual Update Installation: If the above steps do not work, you can try to manually download and install the Windows 11 version 25H2 update from the Microsoft Update Catalog.

If the issue persists after trying these steps, consider checking for any known issues related to Windows 11, version 25H2, as there may be specific compatibility holds or problems affecting your device.

References: