Spybot Search and Destroy is a great spyware tool. It actually removes some of the spyware in Windows OS.
Ad Aware removes anything left by Spybot. You really should run both tools IMO.
SpywareBlaster can be configured to enable every time Windows starts and it disables many of your Active X features (the feeding groud for Spyware). It's a great program and actually helps to keep much of the Spyware off of your computer in the first place.
I use all three programs. Spyware Blaster is an always running background app., the other two I use weekly to keep my PC clean and running fast on the net.