How To Fix .Net Framework 4.7.2 Error 643 0x80070643 In Windows Update

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While trying to install Microsoft .Net Framework 4.7.2 in Windows Update, you may encounter a fatal error 643 (0x80070643) where the update fails and a server reboot results in the same error. Unfortunately this error dates all the way back to .Net Framework 1.x, so it could happen to any version. You could try the Fix Windows Update Errors Tool from Microsoft, but it probably won’t do much. Microsoft also offers a .Net Framework Repair Tool that you can try.

Try The Offline Installer

The first option to try is to download the full offline installer of the .Net Framework you’re trying to install. As of this article, it is .Net Framwork 4.7.2. If the issue is because of Windows Update, then the offline installer might work. When I ran into this issue, the offline installer worked when Windows Update failed.

Check Registry Files For Permissions

  • Use the Windows key + R to open a run command
  • Type regedit.exe and press OK
  • Navigate to: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer
  • Check if following registry keys have correct values:
    MsiExecCA32 should end with \Windows\syswow64\msiexec.exe
    MsiExecCA64 should end with \Windows\system32\msiexec.exe
  • If those are correct, then highlight one and go to Edit > Permissions and verify that SYSTEM and Administrators have Full Control and not just Read permissions
    Repeat for the other key
  • If you had to make changes to the registry, restart the computer or server and try the installation again

Rebuild Your Windows Update SoftwareDistribution Folder

  • Open a command prompt and type: net stop wuauserv
  • Use the Windows key + R to open a run command and type: %windir% and press Enter
  • In the opened folder, rename the SoftwareDistribution folder to SoftwareDistribution.old
  • Open a command prompt and type: net start wuauserv
  • Try to install .NET Framework again

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