Here I use Avast and AVG stuff, I used to use Ad-Aware but not anymore. Something about newer versions white listing certain spyware because the spyware companies threatened them, but my reason for not using it anymore isn't that... I just don't use it these days, that's all. Spybot is powerful but it sure isn't n00b-friendly; yes, on my previous computer it did kill every last bit of Internet advertising, but it wrecked something down the line that made a lot of the interactive stuff on websites completely unusable no matter what I did, even the MSN online games service where all those casual games are. And it still didn't kill the Messenger Service hijack I had at that time.
AVG Free for antivirus... Using both AVG and Avast, both are good but Avast at totally-paranoid maximum protection seriously slows down the entire system, and I have to turn off individual shields when I notice my posts (like this one) are taking so long to process. AVG's guard.exe can get annoying at times as well...