I think I've fixed the registry issue, and I found one main file it had installed (though I suspect there are others lurking), and now I can run .exe files again, so I've installed a second anti-virus program, known to be able to deal with this sucker, and it is doing its deep scanning thing. As is my original anti-virus program, freshly upgraded and updated with as-of-this-morning virus definitions (caught the damn thing last night).
So right now everything seems to be working, and that is good because getting to this point was hard and frustrating.
Also it is raining, so I can't dig on the chicken coop foundation and the poor dog hasn't been outside yet today. He would like us to turn the rain off, please.