Always been an AVG User. My dad managed to make the paid version FREE!! Found out he used the 7.5 serial to put onto the 8.0. But that never worked with mine
I use:
HijackThis
AVG 8.0
Spybot (yes, I like many lines of defence against spywares

HijackThis is actually intended for people who knows their computer's processes but for me, it was easy to pick out things that aren't supposed to be in there then I nuked them in safe mode)
the standard Microsoft Firewall. Thinking of installing a third party firewall because a spyware (continously being nuked) keeps shutting off my firewalls at startups.