I'd like to throw in Spyware Doctor. The trial version gives you unlimited real-time spyware protection, and with my experience with it, its the best spyware remover I've used (with full version)
Spyware doctor is very good. I've used it many times and it picks up a lot of stuff. Spybot, Adaware 2007 and AVG antispyware are also good. For an antivirus I like AVG, Avast and Avira which are all free and do a good job of protecting.
I still like to have windows defender on computers. It's free and doesn't make a foot-print on the computer. Worse come-to-worse, it actually finds something ^_^