How to Fix Installation Failed Error 0x80070643

Fix Windows error 0x80070643 when updates, .NET Framework, or Microsoft Defender fail to install by repairing .NET, resetting updates, and checking WinRE.

Error 0x80070643 means “Installation failed” (a fatal error during installation). Windows Update shows it when an update package starts installing but cannot finish. It most often affects .NET Framework updates, Microsoft Defender definition updates, and Windows Recovery Environment (WinRE) updates. Work through the fixes below in order and check for updates again after each one.

What causes error 0x80070643

• A damaged or partially installed .NET Framework.
• Corrupted Windows Update components or a broken update cache.
• Conflicts with third-party antivirus during installation.
• A recovery partition that is too small for a WinRE update.
• Corrupted system files.
• A pending restart from an earlier update.

Restart your PC first. If an earlier update is waiting for a restart, new updates can fail with this error.

Fix 1: Run the Windows Update troubleshooter

• Windows 11: Go to Settings > System > Troubleshoot > Other troubleshooters, then click Run next to Windows Update.
• Windows 10: Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters, select Windows Update, and click Run the troubleshooter.

Fix 2: Repair .NET Framework

If the failing update mentions .NET Framework, repair it.

1. Download the repair tool

   Download the Microsoft .NET Framework Repair Tool from the official Microsoft website.

2. Run the tool

   Open the tool, accept the license, and let it detect and apply fixes.

3. Restart and retry

   Restart your PC and check for updates again.

You can also toggle .NET Framework off and on: press Windows + R, type optionalfeatures, press Enter, uncheck .NET Framework 3.5, restart, then check it again.

Fix 3: Update Microsoft Defender manually

If the failing update is a Defender definition update (for example, “Security Intelligence Update for Microsoft Defender Antivirus”):

1. Open Windows Security

   Go to Windows Security > Virus & threat protection.

2. Check for updates

   Under Virus & threat protection updates, click Protection updates, then Check for updates.

If you use a third-party antivirus, Defender definition updates may fail because Defender is turned off. In that case the error is usually safe to ignore.

Fix 4: Temporarily disable third-party antivirus

Turn off real-time protection in your antivirus, install the update, then turn protection back on.

Always re-enable your antivirus after installing the update.

Fix 5: Reset Windows Update components

Open Command Prompt as administrator and run:

Command Prompt

net stop wuauserv
net stop bits
net stop cryptsvc
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start msiserver
net start cryptsvc
net start bits
net start wuauserv

Restart your PC and check for updates again.

Fix 6: Repair system files with SFC and DISM

Open Command Prompt as administrator and run these commands one at a time:

Command Prompt

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

Wait for each scan to finish, then restart your PC.

Fix 7: Check the Windows Recovery Environment

If the failing update is a WinRE or recovery update, the recovery partition may be too small. Check its status in an elevated Command Prompt:

Command Prompt

reagentc /info

If Windows RE status shows Enabled, the partition may need more free space for the update. Follow Microsoft’s official instructions for resizing the recovery partition for your update’s KB number.

Resizing partitions can cause data loss if done incorrectly. Back up your files first, and skip this fix if you are not comfortable working with disk partitions.

Fix 8: Install the update manually

1. Find the KB number

   Go to Settings > Windows Update > Update history and note the KB number of the failed update.

2. Download the update

   Search for the KB number in the Microsoft Update Catalog and download the package that matches your Windows version and system type.

3. Install it

   Run the downloaded file and restart your PC when prompted.

Frequently asked questions

Is error 0x80070643 harmful to my PC?

No. It means one update did not install. Your PC keeps working, but you may miss security fixes until the update installs.

Why does the same update keep failing?

Windows retries failed updates automatically. If the cause is not fixed, such as a broken .NET install or a small recovery partition, the update fails each time.

Can I hide an update that keeps failing?

Yes. You can pause updates from Settings > Windows Update, but fixing the cause is the better option so you stay protected.

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