I got a notice to update my BOINC sw so I did try. However, after several apparently successful downloads, it refused to accept the boinc.msi that was downloaded. I searched for others and they were not acceptable either.

I tried to uninstall what ever version I have ater a partial install (I started out with the 6.12.26 version and going to the .33) but the uninstaller also failed for the same reason.

I have repaired .26 after restarting and will continue using it until I hear its OK to use .33

If your error was something in the magnitude of "Windows Installer Error 1706: Setup cannot find the required files / 1714: older version cannot be removed / BOINC.msi cannot be found / The feature you are trying to use is on a network resource that is unavailable.", then repairing the previous version is exactly what you should've done. The previous BOINC.msi was corrupt, repairing the installation fixed that.

You can now install 6.12.33 without problems.
Mind, this is a Windows problem, not so much a BOINC problem. It's Windows losing sight of where it put the installation file.

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Thank you Jord. That did it.