> For the complete documentation index, see [llms.txt](https://fixerrors-now.gitbook.io/fixerrors-now-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://fixerrors-now.gitbook.io/fixerrors-now-docs/getting-fatal-error-during-installation-0x8007064/getting-fatal-error-during-installation-0x80070643.md).
# Getting Fatal error during installation (0x80070643)
#### What is this Error?
Error code **0x80070643** means “Fatal error during installation.”\
It usually appears when Windows fails to install an update. This is a common issue on both Windows 10 and Windows 11.
#### When Does This Error Appear?
This error mostly shows up in these situations:
* While installing Windows Updates
* During Microsoft Defender security intelligence updates
* When installing .NET Framework updates
* Sometimes with Windows Recovery Environment (WinRE) related updates
#### Why Does This Error Happen?
Here are the most common reasons:
* Windows Update cache is corrupted
* Important system files are damaged
* Not enough free space in the Recovery partition
* Microsoft Defender definitions are stuck or corrupted
* Third-party antivirus is blocking the update
* .NET Framework has issues
#### How to Fix It (Step-by-Step)
Follow these steps one by one. Most people solve the problem with the first few steps.
**Step 1: Restart Your PC**\
Restart your computer and check for updates again. Sometimes a simple restart fixes the issue.
**Step 2: Run Windows Update Troubleshooter**
* Go to **Settings → System → Troubleshoot → Other troubleshooters**
* Find **Windows Update** and click **Run**
* Apply the fixes and restart your PC
**Step 3: Reset Windows Update Components**\
Open **Command Prompt as Administrator** and run these commands one by one:
text
```
net stop bits
net stop wuauserv
net stop cryptsvc
net stop msiserver
ren %Systemroot%\SoftwareDistribution SoftwareDistribution.old
ren %Systemroot%\System32\catroot2 catroot2.old
net start bits
net start wuauserv
net start cryptsvc
net start msiserver
```
After running all commands, restart your computer and try updating again.
**Step 4: Repair System Files**\
Open Command Prompt as Administrator again and run:
text
```
DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow
```
Wait for both processes to complete, then restart your PC.
**Step 5: Extra Fixes (If Needed)**
* Temporarily disable your antivirus and try updating
* If the failed update is related to Microsoft Defender, reset Defender definitions
* Make sure your C: drive has enough free space
#### Final Tip
In most cases, **Step 2, Step 3, and Step 4** are enough to fix the 0x80070643 error. Follow the steps carefully and the update should install successfully.
---
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