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Windows 11

Windows 11 Install Error 0x800f0991

When Windows Update shows Install error 0x800f0991, DISM and cache resets often fail. Use Recovery Reinstall now, which keeps apps and files.

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Last checked
Sep 6, 2026
Applies to
Windows, Desktop
Fix status
Community Confirmed
Fastest useful check

Quick answer

Install error 0x800f0991 means Windows Update could not finish a cumulative or security update because servicing metadata or payload files are incomplete. After SoftwareDistribution resets, DISM, and SFC fail, open Settings → System → Recovery → Fix problems using Windows Update → Reinstall now. That repair keeps apps, files, and settings. Then check Windows Update again. Managed work PCs may not show the Recovery option.

On this page

What we're seeing

  • The Update history line is Install error - 0x800f0991, often after a monthly security update such as KB5074109 or KB5077181 downloads and then fails while installing.
  • Microsoft Q&A threads from January through March 2026 report the same code across different KBs when the Component Based Servicing store cannot validate the package.
  • People in those threads say renaming SoftwareDistribution and catroot2, running DISM RestoreHealth, SFC, and even a Catalog MSU still failed, then Recovery Reinstall now succeeded.
  • Microsoft documents Fix problems using Windows Update as a keep-apps repair for Windows Update problems. It does not publish a dedicated 0x800f0991 article, so this guide treats the Recovery path as community-confirmed for this exact code.
  • A different update error, a feature-update setup failure, or a blue-screen during install is outside this fingerprint.

Start here

Try these first

Fix 1

Confirm Install error 0x800f0991

Community Confirmed

Match the exact code before starting a repair reinstall. Nearby codes such as 0x800f0983 appear in the same waves and may share the leftover, but this guide is for 0x800f0991.

  1. Open Settings → Windows Update → Update history and find Install error - 0x800f0991 on a failed cumulative or security update.
  2. Note the KB number shown next to the failure. The leftover below is for this install code, not for a separate feature-update or Store error.
  3. Confirm the PC has enough free space on C: (community reports often cite tens of gigabytes) and stays on power and internet for a long repair.

Applies to Windows, Desktop

Fix 2

Try light update resets once

Possible Workaround

Microsoft Advisors still recommend a single SoftwareDistribution reset and DISM or SFC pass. Independent reports for 0x800f0991 often say those steps do not clear the code, so treat them as a short first pass, not a loop.

  1. Run the Windows Update troubleshooter once from Settings → System → Troubleshoot → Other troubleshooters, then retry the update.
  2. If it still fails, open an elevated Command Prompt, stop the Windows Update related services, rename C:\Windows\SoftwareDistribution to SoftwareDistribution.old and C:\Windows\System32\catroot2 to catroot2.old, restart the services, reboot, and check for updates once.
  3. Optionally run DISM.exe /Online /Cleanup-image /Restorehealth, then sfc /scannow, reboot, and retry once. If 0x800f0991 returns, stop repeating these resets and go to Recovery Reinstall now.

Applies to Windows, Desktop

Fix 3

Use Recovery Reinstall now

Community Confirmed

Across January–March 2026 Microsoft Q&A threads for this exact install error, people who had already failed DISM and cache resets reported success with Settings → System → Recovery → Fix problems using Windows Update → Reinstall now. Microsoft says the process reinstalls the current Windows version while preserving apps, files, and settings.

  1. Plug into power and stay on a stable internet connection for the whole run. Expect roughly one to two hours on many PCs.
  2. Open Settings → System → Recovery. Under Fix problems using Windows Update, select Reinstall now.
  3. Choose whether the PC may restart automatically about 15 minutes after install finishes, then select OK and let the repair download and install.
  4. After the restart, open Windows Update and confirm the previously failing update no longer shows Install error - 0x800f0991.
  5. If Windows.old appears afterward, free space later with Disk Cleanup or Storage settings once you are sure apps still work.

Applies to Windows, Desktop

Fix 4

In-place repair from a matching Windows 11 ISO

Community Confirmed

Microsoft notes that Fix problems using Windows Update can be missing on managed work or school PCs and on some older builds. When Recovery is unavailable, Q&A Advisors for 0x800f0991 point to an in-place repair from an official Windows 11 ISO while keeping personal files and apps.

  1. Download a current Windows 11 ISO from Microsoft that matches your edition and architecture.
  2. Mount the ISO in Windows, run setup.exe, and choose to keep personal files and apps.
  3. Finish setup, reboot as prompted, then open Windows Update and install any remaining updates.
  4. If the PC is managed by work or school policies, ask IT before changing update paths or running an ISO repair.

Applies to Windows, Desktop

Device notes

Windows
This fingerprint is for Windows 11 Update history showing Install error - 0x800f0991. Keep the PC on AC power. Managed devices may hide Recovery Reinstall now.
Desktop
Laptops and desktops both hit this code on monthly cumulative updates. Free space on C: and a stable network matter more than the form factor.

Official information

Checked on 6 September 2026, Microsoft Support documents Fix problems using Windows Update → Reinstall now as a keep-apps repair for Windows Update problems, including after an update installation fails. Microsoft does not publish a dedicated support article that names 0x800f0991. Independent Microsoft Q&A reports from January–March 2026 match this exact install error on monthly security updates and repeatedly clear it with Recovery Reinstall now after DISM and cache resets fail.

Sources

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