Thank you for your suggestion. I downloaded and ran your program, and then rebooted, but the Windows 8.1 update still claims that Avast supposedly needs to be uninstalled, and thus will not complete. I wish that I could do the 8.1 update in Windows Safe Mode; but, of course, Windows will not allow me to do that.

So, do you or anyone else, particularly somebody working for Avast (nothing personal), have any other ideas on how to resolve this conundrum? Thank you again for the suggestion.