how to fix this update error show always in Windows 11 Insider Preview 29639.1000 (rs_prerelease)

Try these steps in order for a Windows 11 Insider update that repeatedly fails after restart:

1. Run the Windows Update troubleshooter again from Start > Settings > System > Troubleshoot > Other troubleshooters > Windows Update > Run.
2. Restart the PC.
3. Go to Start > Settings > Windows Update > Check for updates and try the update again.

If it still fails, use the advanced repair steps below.

4. Open Command Prompt as administrator.
5. Run these commands one at a time:

net stop bits
net stop wuauserv
ren %systemroot%\softwaredistribution softwaredistribution.bak
ren %systemroot%\system32\catroot2 catroot2.bak
net start bits
net start wuauserv

6. Restart the PC and try Windows Update again.

If the issue continues, repair system files:

7. Open Command Prompt as administrator.
8. Run:

DISM.exe /Online /Cleanup-image /Restorehealth
sfc /scannow

9. Wait for sfc to reach 100%, then try the update again.

Additional checks that can help with upgrade failures:

• Disconnect nonessential external hardware such as USB drives, printers, scanners, speakers, and external hard drives.
• Temporarily uninstall third-party antivirus or security software before updating, then reinstall it after the device is up to date. Make sure installation media or product keys are available first.
• If a previous installation cleanup is pending, restart the device and try setup again.

Warning: the Command Prompt repair steps require administrator permissions. Renaming Windows Update folders and running DISM/SFC are standard repair actions, but they should be entered exactly as shown.

References:

• Windows Update Troubleshooter
• Troubleshoot problems updating Windows
• Get help with Windows upgrade and installation errors