Also received a message from Bumpkin; don't know why it didn't show up here in the forum. I had already tried that; it is one of the free password crackers I mention above.
I managed to resolve the problem; not sure how. Using the usual Manage Accounts window, I reset the Admin account password (yet again), and for whatever reason, this time it worked !
Problem solved. I'll create the backup disk now.
Thanks to all for your help.