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
Step#1 - Capture Process Monitor Trace 1. Download and run Process Monitor. Leave this running while you perform the next steps.
2. Try unchecking .NET Framework 3.5 just like you have in the past.
3. Stop Process Monitor as soon as it fails. You can simply do this by clicking the magnifying glass on the toolbar as shown below.
4. Select the File menu...Save... and save the file to your desktop. This is likely the default location. The name (unless changed) will be LogFile.PML. This is fine.
5. Zip up and attach the LogFile.PML file as well as your CBS.log
Unchecking .NET 3.5 failed.
Process monitor executed as described.
Logfile as "Logfile_20181125.pml" compressed and uploaded to Google Drive.
CBS folder compressed and uploaded to Google Drive as "CBS_20181125.ZIP"
Would you be willing to try upgrading to Win10? I'm asking because this is a very complex fix and I wouldn't want to waste your time fixing it there's an easier way. :)
To be honest I would like to avoid upgrading as long as possible...
If the fix takes too long, or too difficult to worth it, I'd rather return to a previous state when .NET was worked more or less even .NET updates not working.
I have got a warning from Repair Windows, that I'm not in safe mode, so I can choose to continue with risks or reboot to safe mode (See screenshot).
What to choose?
Repair Windows executed in Safe Mode as admin, only repair No.16 was checked and PC restarted after repair.
Windows Update found 3 recommended updates, KB4054530, KB4457918 and KB4467240.
Update was failed for all. Error Code 643 for KB4054530, and Error Code 2 for KB4457918 and KB4467240.