Free Antivirus Program for ME

Since the free edition of Avast stopped supporting Windows ME, I found this
quite suitable substitute:

http://www.clamwin.com/

Depending on one's attitude towards OpenSource software,
I personally don't have any objections, if quality is the main objective,
and I found that to be the case.

OTOH Avast is giving me a heap of trouble with these popups and trying to
induce upgrading. I tried to delete the program, but to no avail, it just
will not let me.
Is there a way to tweak the registry without doing any harm?

Any help appreciated,

Harry.