I've actually been quite impressed by the scanning capabilities of a program called "GIANT Anti-Spyware." It recently got a good review from Gibson's site. (Not that Gibson's site is exactly the end-all of honesty and disclosure, but it's usually an interesting place to glance over.)
Anyhow, I'd never heard of "GIANT" software before, so I decided to see what it was all about on a friend's hosed up PC earlier today. After a couple runs through with the free download version, the machine was quite a bit better off. I don't know if I'd bother to buy it, but for a quick clean-up it seemed to fare quite well.
http://www.giantcompany.com/
