FrankM

Here is a fix for that problem.

A telephone service rep named Murray at HP told me the System Restore
program must be corrupted and the only way to resolve the issue was to use
the System Recovery Disks to take the PC back to when-new condition.

Before I was ready to take that drastic action I phoned HP again for a
second opinion and got a different technician, Naomi. She tried using Safe
Mode to run System Restore. It works fine from there. The program was NOT
corrupted.

It is a little inconvenient to run System Restore from Safe Mode but far
preferable to reinstalling all my programs after using Recovery Disks,
especially with no guarantee that Restore would work even then. The suspicion
is that something else I have running is conflicting with the Restore
program. But, hey, as long as it works from Safe Mode, I am content.

I post this answer for the benefit of anyone faced with the same issue.