Funny thing, someone at work brought in their home computer to me last week, said it was super slow, probably had a virus.
So I took a look, and oddly enough, 100% clean. Super clean in fact, because there were 4 full AVs running, and when combined with multiple IE toolbars and a few other things, slowness ensued in a big way.
Uninstalled a bunch of them, updated MS Security Essentials, ran all the Windows Updates and such, and it left about 5x faster. (Though with some more memory it'd be 50x faster)
First time I've seen no virus and too many AVs.
