How to fix a broken [.NET framework in?] Windows 11

I have a relatively new PC, just over a year old (Jan 24), that came freshly installed with Windows 11 pro (currently 23H2 22631.4890). However it now rolls-back any attempt to update to Windows version 24H2 with the generic error 0xc1900101 . In an attempt to fix this, I tried to run the Windows Setup Diagnostic Tool but that refuses to load, complaining that: Please set registry key HKLM\Software\Microsoft.NETFramework\InstallRoot to point to the .net framework install location Of course, there is such a registry key, with value C:\Windows\Microsoft.NET\Framework64 , a location which exists

Question by Rob on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.