update install failed

Question

2026-01 Security Update (KB5074109) (26200.7623) failed to install. Install error - 0x800f0991 - please help. new computer win 11 Pro - please help. retried several times always same result.

Answer 1

Hello, thank you for reaching out to Microsoft Q&A.

To run the Windows Update Troubleshooter - Go to Start > Settings > System > Troubleshoot > Other troubleshooters > Windows Update > Click Run.

Once the troubleshooter is finished running, restart your computer and install the updates.

If you are still having trouble, run the System File Checker Utility scan as suggested by AI in the reply above.

DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Important- Run these commands in a Command Prompt (Administrator) Window.

If the issue persists, do a repair reinstall from the Recovery Settings.

Go to Start > Settings > System > Recovery > Fix problems using Windows update.

Select 'Reinstall now.

This will download the repair version of the existing OS on the Windows Update page.

Download and install the repair version.

Let me know if you still need more help.

---

Answer 2

To address the installation error 0x800f0991 for the January 2026 Security Update (KB5074109) on your Windows 11 Pro device, you can follow these troubleshooting steps:

1. Run the Windows Update Troubleshooter: Navigate to Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update, and run the troubleshooter to identify and resolve potential issues.
2. Check for Pending Updates: Ensure that all other updates are installed, as some updates may depend on others being applied first.
3. Use the DISM Tool: Open Command Prompt with administrative privileges and execute the following commands:
   • DISM /Online /Cleanup-Image /CheckHealth
   • DISM /Online /Cleanup-Image /ScanHealth
   • DISM /Online /Cleanup-Image /RestoreHealth This process can help repair the Windows image and resolve update problems.
4. Run System File Checker: Execute sfc /scannow in an elevated Command Prompt to scan for and fix corrupted system files.
5. Manual Installation: If the issue continues, consider manually downloading the update from the Microsoft Update Catalog using the KB number and installing it directly.
6. Contact Microsoft Support: If none of the above solutions work, reaching out to Microsoft Support may provide additional assistance.

After trying these steps, keep an eye on your system to ensure the update status is resolved.