Back to the drawing board! :'(
My husband announced this morning that my "new" system does not work. He had tried to run an attachment through the folder that I put on his desktop to hold files that need a second run through the virus checker.
When I tred to do it ... it wouldn't work. There is no sign of the path to his desktop!
This is the screen I'd get.

So, I got rid of his Administrator status and gave his side a password ... all sorts of things. Nothing worked.
Then the light came on! All I needed to do was uncheck that box that says it might interfere with the program (which it certainly was!) .... and voila! I could run AVAST through the attachment in the folder. Before I did that ... there was no sign of any of the folders on the desktop.
So, I've been able to remove the Administrator designation from the other users of the computer, and done away with the passwords.
At this point in this saga you have likely all totally lost interest

... but I'm like a cat with a rat till I solve a "problem."
Why my "other" new system worked so well the other day ... and today it didn't work at all ... I have absolutely no idea!
Anyhow ... the saga continues ...
Nan