I use Ad aware to blast spy ware (and spy bot sometimes) but be wary there is one "ad" program which attaches itself to a registry file (userinit) and when you erase it with ad aware specifically it corrupts your registry. So make sure you have back ups.

I also use xp anti spy to seal up the holes after I clean the system its very handy and doesnt "run" so it doesnt use up ram, its sort of a "one shot" program although you can change any of the programs options at any time its only active in memory while its open. (like a normal program) I highly recommend it if you use any version of XP (home, corp etc etc) It's basically shut out all but some cydoor programs which I dont even mind as their are only 8 of them and they dont collect info unless I click on certain websites. So I just leave em. (they dont run in memory either so "meh" I leave em).

Hope that helps a bit. I've heard spy blaster is ok , but doesnt clean near as well as the others but safely clears out quite a few. Never used it myself though.