Cumulative Update for Windows 11 Insider Preview (10.0.26120.4441) (KB5060816) Install error - 0x800f0991

Question

I have been getting the following error for about a month now when doing windows updates

Cumulative Update for Windows 11 Insider Preview (10.0.26120.4441) (KB5060816) downloads fine but when installing it usually gets Install error - 0x800f0991 around 40% of the installation

Windows troubleshooting does not detect any problems.

Answer 1

Hi Roxphine,

If a patch gets stuck during installation, I highly recommend trying a manual install using DISM. This method can help narrow down the issue, as DISM sometimes bypasses hidden problems that may block updates.

Before proceeding, it’s a good idea to check the system's health by running these commands in Command Prompt (Admin):

DISM /Online /Cleanup-Image /CheckHealth

DISM /Online /Cleanup-Image /ScanHealth

DISM /Online /Cleanup-Image /RestoreHealth

SFC /scannow

DISM /Cleanup-Image /StartComponentCleanup /ResetBase

These steps help detect and fix any underlying issues that could be interfering with updates.

Once that’s done, you can manually install the update:

1. Download the update package from the Microsoft Update Catalog and extract the .cab file.
2. Run this command in CMD (Admin) to install the patch:

dism /online /add-package /packagepath:"X:\path\to\update.cab"

(Make sure to replace the path with the actual location of your .cab file.)

Hope this helps get your system back on track!