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# 0x80070643 ERROR_INSTALL_FAILURE: Fix Windows Update Install Error

> Fix Windows Update error 0x80070643 (ERROR_INSTALL_FAILURE) in Windows 10 and 11, including KB5034441 WinRE, .NET Framework, and Defender update failures.

Windows Update error **0x80070643** (`ERROR_INSTALL_FAILURE`) means an update downloaded correctly but **failed while installing**. It shows up most often with **.NET Framework** updates, **Microsoft Defender** definition updates, and the **Windows Recovery Environment (WinRE)** security update KB5034441. This guide explains each case and walks you through the fixes, starting with the quickest.

<Info>
  **Quick answer:** Restart your PC, run the Windows Update troubleshooter, then reset the Windows Update cache (Fix 3). If the failed update is **KB5034441**, see Fix 6, because that error comes from a WinRE partition that is too small.
</Info>

## What does error 0x80070643 mean?

The code **0x80070643** stands for `ERROR_INSTALL_FAILURE`, which means **"Fatal error during installation."** Windows got the update files, but the installer stopped before it could finish.

You may see messages like:

* `There were some problems installing updates... (0x80070643)`
* `2024-01 Security Update for Windows 10 (KB5034441) - Error 0x80070643`
* `Security Intelligence Update for Microsoft Defender Antivirus - Error 0x80070643`
* `.NET Framework update failed - 0x80070643`

## Common causes

* **WinRE recovery partition too small** (the classic KB5034441 problem)
* **Damaged .NET Framework** installation
* **Corrupted Windows Update cache**
* **Damaged system files**
* **Third-party antivirus** conflicting with Microsoft Defender updates
* The **Windows Installer** service not running properly

## How to fix error 0x80070643

Try the fixes in order. Restart your PC after each one and check Windows Update again.

### Fix 1: Restart and retry the update

1. Restart your PC (choose **Restart**, not Shut down).
2. Go to **Settings > Windows Update** and select **Check for updates** or **Retry**.

Sometimes a pending installation blocks the next one, and a restart clears it.

### Fix 2: Run the Windows Update troubleshooter

<Steps>
  <Step title="Open troubleshooter settings">
    * **Windows 11:** Go to **Settings > System > Troubleshoot > Other troubleshooters**.
    * **Windows 10:** Go to **Settings > Update & Security > Troubleshoot > Additional troubleshooters**.
  </Step>

  <Step title="Run the Windows Update troubleshooter">
    Select **Run** next to **Windows Update** and apply any fixes it suggests.
  </Step>
</Steps>

### Fix 3: Reset Windows Update components

Clearing the update cache removes broken installer files.

Open **Command Prompt as administrator** and run these commands one by one:

```bash Reset Windows Update theme={null}
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
```

Restart your PC and check for updates.

### Fix 4: Repair system files with DISM and SFC

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

```bash Repair system files theme={null}
DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow
```

Wait for both scans to finish, restart your PC, and try the update again.

### Fix 5: Repair .NET Framework

If the failed update mentions **.NET Framework**, repair it first.

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

  <Step title="Run the tool">
    Run the tool, accept the terms, and let it apply the recommended fixes.
  </Step>

  <Step title="Turn .NET 3.5 off and on (optional)">
    Press **Win + R**, type `optionalfeatures`, and press **Enter**. Uncheck **.NET Framework 3.5**, select **OK**, restart, then check it again and select **OK**.
  </Step>

  <Step title="Retry the update">
    Restart your PC and run Windows Update again.
  </Step>
</Steps>

### Fix 6: Fix KB5034441 (WinRE partition too small)

On Windows 10, the security update **KB5034441** fails with 0x80070643 when the **recovery (WinRE) partition** does not have enough free space. Microsoft's fix is to make that partition about **250 MB** larger.

<Warning>
  This fix changes disk partitions. **Back up your important files first.** If you are not comfortable with disk commands, skip this fix. The error does not harm your PC, and your other updates still install normally.
</Warning>

<Steps>
  <Step title="Check the WinRE status">
    Open **Command Prompt as administrator** and run:

    ```bash theme={null}
    reagentc /info
    ```

    Note the **Windows RE location** line. It shows the disk and partition number, for example `harddisk0\partition4`.
  </Step>

  <Step title="Disable WinRE">
    ```bash theme={null}
    reagentc /disable
    ```
  </Step>

  <Step title="Shrink the Windows partition by 250 MB">
    Run `diskpart`, then:

    ```text theme={null}
    list disk
    sel disk 0
    list part
    sel part 3
    shrink desired=250 minimum=250
    ```

    Replace `0` with your OS disk and `3` with your Windows (C:) partition number.
  </Step>

  <Step title="Delete and recreate the recovery partition">
    Still in diskpart, select the recovery partition and recreate it:

    ```text theme={null}
    sel part 4
    delete partition override
    create partition primary id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
    gpt attributes=0x8000000000000001
    format quick fs=ntfs label="Windows RE tools"
    exit
    ```

    Replace `4` with your recovery partition number. On **MBR** disks, use `create partition primary id=27` instead and skip the `gpt attributes` line.
  </Step>

  <Step title="Enable WinRE again">
    ```bash theme={null}
    reagentc /enable
    reagentc /info
    ```

    Check that **Windows RE status** shows **Enabled**, then run Windows Update again.
  </Step>
</Steps>

<Tip>
  To check your disk type, run `diskpart`, then `list disk`. If there is an asterisk (\*) under **Gpt**, your disk is GPT. Otherwise it is MBR.
</Tip>

### Fix 7: Fix Microsoft Defender update failures

If the failed update is a **Security Intelligence Update for Microsoft Defender**:

1. Temporarily turn off or uninstall any third-party antivirus.
2. Open **Windows Security > Virus & threat protection > Protection updates** and select **Check for updates**.
3. If it still fails, open **Command Prompt as administrator** and run:

```bash Update Defender definitions theme={null}
"%ProgramFiles%\Windows Defender\MpCmdRun.exe" -RemoveDefinitions -DynamicSignatures
"%ProgramFiles%\Windows Defender\MpCmdRun.exe" -SignatureUpdate
```

### Fix 8: Restart the Windows Installer service

<Steps>
  <Step title="Open Services">
    Press **Win + R**, type `services.msc`, and press **Enter**.
  </Step>

  <Step title="Restart Windows Installer">
    Find **Windows Installer**, right-click it, and select **Start** (or **Restart** if it is already running).
  </Step>

  <Step title="Retry the update">
    Go back to Windows Update and try again.
  </Step>
</Steps>

### Fix 9: 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 from Microsoft Update Catalog">
    Visit the [Microsoft Update Catalog](https://www.catalog.update.microsoft.com), search for the KB number, and download the version for your system (x64 or ARM64).
  </Step>

  <Step title="Install it">
    Double-click the downloaded file and follow the prompts. Restart when asked.
  </Step>
</Steps>

## How to prevent error 0x80070643

* Use only one antivirus program at a time.
* Keep at least 20 GB of free space on drive C:.
* Do not turn off your PC while updates are installing.
* Run `DISM` and `sfc /scannow` every few months to keep system files healthy.

## Frequently asked questions

<AccordionGroup>
  <Accordion title="What is ERROR_INSTALL_FAILURE?">
    It is the internal name for error 0x80070643. It means an update was downloaded but failed during installation.
  </Accordion>

  <Accordion title="Why does KB5034441 fail with 0x80070643?">
    The recovery (WinRE) partition on your PC is too small for the update. Enlarging it by about 250 MB (Fix 6) solves the problem.
  </Accordion>

  <Accordion title="Is it safe to ignore error 0x80070643?">
    If it only affects KB5034441, your PC keeps working normally and other updates still install. For .NET or Defender updates, fix it so you keep getting security protection.
  </Accordion>

  <Accordion title="Will these fixes delete my files?">
    Fixes 1 to 5 and 7 to 9 do not touch your files. Fix 6 changes disk partitions, so back up your files before trying it.
  </Accordion>

  <Accordion title="Does 0x80070643 happen on Windows 11?">
    Yes. It can appear on both Windows 10 and Windows 11 for .NET and Defender updates. The KB5034441 WinRE issue mainly affects Windows 10.
  </Accordion>
</AccordionGroup>


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