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# 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.

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

## 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.

<Steps>
  <Step title="Download the repair tool">
    Download the **Microsoft .NET Framework Repair Tool** from the official Microsoft website.
  </Step>

  <Step title="Run the tool">
    Open the tool, accept the license, and let it detect and apply fixes.
  </Step>

  <Step title="Restart and retry">
    Restart your PC and check for updates again.
  </Step>
</Steps>

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"):

<Steps>
  <Step title="Open Windows Security">
    Go to **Windows Security > Virus & threat protection**.
  </Step>

  <Step title="Check for updates">
    Under **Virus & threat protection updates**, click **Protection updates**, then **Check for updates**.
  </Step>
</Steps>

<Note>
  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.
</Note>

## Fix 4: Temporarily disable third-party antivirus

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

<Warning>
  Always re-enable your antivirus after installing the update.
</Warning>

## Fix 5: Reset Windows Update components

Open **Command Prompt** as administrator and run:

```bash Command Prompt theme={null}
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:

```bash Command Prompt theme={null}
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:

```bash Command Prompt theme={null}
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.

<Warning>
  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.
</Warning>

## Fix 8: Install the update manually

<Steps>
  <Step title="Find the KB number">
    Go to **Settings > Windows Update > Update history** and note the KB number of the failed update.
  </Step>

  <Step title="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.
  </Step>

  <Step title="Install it">
    Run the downloaded file and restart your PC when prompted.
  </Step>
</Steps>

## Frequently asked questions

<AccordionGroup>
  <Accordion title="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.
  </Accordion>

  <Accordion title="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.
  </Accordion>

  <Accordion title="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.
  </Accordion>
</AccordionGroup>

## Related errors

<CardGroup cols={2}>
  <Card title="Fix 0x80070422" icon="wrench" href="/index">
    Fix Windows Update errors caused by disabled services.
  </Card>

  <Card title="Fix 0x80070005" icon="lock" href="/fix-0x80070005-access-denied">
    Fix access denied errors in updates and installs.
  </Card>

  <Card title="Network Failure Error" icon="wifi" href="/windows-update-network-failure">
    Fix Windows Update connection and download errors.
  </Card>
</CardGroup>


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