It has taken a while to get both computers updated today. I updated to the new version of Spybot and dumped AdAware on the other computer (it has been absent from mine for several months now, since it introduced the new version. THAT is what slowed my computer too much).
My computer is still being scanned and it has gone over an hour. No way I would do this every day; I'll fiddle with what it scans and how often. I have my son's computer scanning now, and will set it by default to not scan. We'll do it manually. It's finding a lot of junk, but I also expect to have to log on to some sites after if finishes.