essexboy
Many thanks for your help.
I wish I thought of that simple solution, because I had encountered and used it before for other apps. I wish I could test it, but I already got impatient and scared and uninstalled avast and substituted it with a competitor's product. I hope to remember what you told me for next time I have one of these problems, for other programs and for avast. I found Avast far more useful than the competition when I had it and still have not found an adequate substitute.
One possible clue that I have about what may have gone wrong is that a few weeks ago I made an avast screensaver scan shortcut and used it a few times. I then deleted it, and fine tuned the options for the screensaver scan, but unfortunately for some days I did not pay attention for anything out of the ordinary at the bottom of the scans choices sheet. A week or two later I noticed the offending item. Thus, maybe independently using the screensaver scan caused the duplicate and so it was ok? Because I am very busy, currently I do not feel like trying to replicate the problem, but if it comes up again I will try to remember to report right here. I wish I knew, if The Rabbit also made a screensaver shortcut and used it prior to his duplicate appearing.
To everyone who even only read posts in the thread,
Thank you for your time.