0x80070643
Moderate
Microsoft · Windows
.NET Framework update installation failed, or Windows Defender definition update issue. The update installer (msiexec.exe) returned an error during package installation.
Quick Answer
Error code 0x80070643 on your Microsoft Windows means: .NET Framework update installation failed, or Windows Defender definition update issue. The update installer (msiexec.exe) returned an error during package installation.. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Open Command Prompt as Administrator and run: sfc /scannow — wait for the scan to complete and note any errors found.
2
Run DISM to repair the component store: DISM /Online /Cleanup-Image /RestoreHealth — this can take 15-30 minutes.
3
Manually repair .NET Framework: Open Control Panel > Programs and Features > Turn Windows features on or off. Uncheck .NET Framework 3.5 and .NET Framework 4.x, click OK, restart, then re-enable them.
4
Reset Windows Update components: Stop the BITS, wuauserv, appidsvc, and cryptsvc services by running: net stop bits && net stop wuauserv && net stop appidsvc && net stop cryptsvc. Then rename C:\Windows\SoftwareDistribution to SoftwareDistribution.old and C:\Windows\System32\catroot2 to catroot2.old. Restart the services with net start commands.
5
If the error is specifically for Windows Defender definitions, open Windows Security > Virus & threat protection > Check for updates, or download the latest definitions manually from the Microsoft Malware Protection Center.
6
Download and run the .NET Framework Repair Tool from Microsoft (NetFxRepairTool.exe) to fix installation issues.
7
If all else fails, download the specific KB update from the Microsoft Update Catalog (catalog.update.microsoft.com) and install it manually using the standalone installer.
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
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