Windows 11security update will not install - how do i fix this ?

Question

Windows 11security update will not install - how do i fix this ?

alan waddell 5

The message in the Windows update page says: 2026-01 Security Update (KB5074109) (26200.7623) - Install error - 0x800f0991 . What do i need to do to fix this install error ? (Windows 11 . BIOS DATE 25 / 04 / 2025)

Deacon Paul Duckro 20 Reputation points

2026-01-18T16:59:37.1433333+00:00

I found this error also in the December Security Update. After some looking around, I noticed that the update was in fact installed. The problem was that Windows Update was trying to install it again and again. I even deleted the installed update and tried to let Windows Update install it, with no positive effect. I manually re-installed the update from the Catalog, but the automated process continued to try to re-install it, without success. Note that this issue is happening only on a new Dell laptop. It is not happening on my old Lenovo laptop.

3 answers

Your answer

Deacon Paul Duckro 20 Reputation points

2026-01-18T16:59:37.1433333+00:00

I found this error also in the December Security Update. After some looking around, I noticed that the update was in fact installed. The problem was that Windows Update was trying to install it again and again. I even deleted the installed update and tried to let Windows Update install it, with no positive effect. I manually re-installed the update from the Catalog, but the automated process continued to try to re-install it, without success. Note that this issue is happening only on a new Dell laptop. It is not happening on my old Lenovo laptop.

Answer 1

Alan, the error 0x800f0983 was shown to lots of people after trying to install the KB5077181 February monthly patch for Windows 11. Later, the error switched to the number with 991 at the end, you just got the same problem a month earlier than we did for some reason. All these people including me with my Vivobook tried all possible deletion of SoftwareDistribution, catroot2 folders, restarting WU related services, SFC, DISM with Scanhealth, Checkhealth, Restorehealth, without source, with source at Windows Update, and even with the full ISO source, and the MSU patch from Microsoft Catalog. Everything fails.

However, all ten+ people who have tried have succeeded a miraculous cure using a new Windows 11 tool. It is in Settings, System (in the left sidebar), Recovery (a right sidebar option), and "Fix Problems Using Windows Update" (second tool in the right sidebar). Click "reinstall now" and don't be afraid of the terrifying verb. It preserves apps, files, and settings. Except for asking whether you want an automatic restart at the end, it is nothing else than a Windows Update process, just the patch is called "Windows 11 Recovery Edition". And it takes twice as long because it is really installing even things that the regular light Windows Update (incorrectly) decides that your PC does not need (that is really why these 800f errors appear). For me, a fast WiFi downloaded it in 10 minutes, followed by 55 minutes "installing" inside Windows, otherwise like a regular patch, and just 5 minutes of black-screen installation phase outside Windows, plus 2 extra minutes after the first login to a user profile. And when it was completed, I had the newest post-February-patch level of Windows 11.

You should simply do it, trust me, you are no longer a beta tester, this tool simply works (10 out of 10 confirm) and frankly speaking, it may be better to use it after any error of Windows Update.

Deacon Paul Duckro 20 Reputation points

2026-02-18T14:41:16.9766667+00:00

I tried this and, except for having to reinstall the desktop wallpaper, it seems to have done the trick. No one else--local IT, Dell support, Microsoft support--had come up with it. Thank you for posting the idea.

Answer 2

WindowsStinks 0

How about you guys make an operating system that actually works. All of a sudden my updates are failing. Security updates mind you. But its cool, i will be installing linux because you guys are total trash

0 comments

Answer 3

To resolve the installation error 0x800f0991 for the Windows 11 security update (KB5074109), you can try the following steps:

Run Windows Update Troubleshooter: Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update and run the troubleshooter.
Check for Corrupted System Files: Open Command Prompt as an administrator and run the command sfc /scannow to check for and repair corrupted system files.
Use DISM Tool: If the issue persists, you can use the Deployment Imaging Service and Management Tool (DISM). Open Command Prompt as an administrator and run the following commands:
- DISM /Online /Cleanup-Image /CheckHealth
- DISM /Online /Cleanup-Image /ScanHealth
- DISM /Online /Cleanup-Image /RestoreHealth
Restart Your Computer: After running these commands, restart your computer and try to install the update again.
Manual Installation: If the update still fails, you can download the update manually from the Microsoft Update Catalog and install it.

If these steps do not resolve the issue, consider checking for any pending updates or contacting Microsoft support for further assistance.

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