Don't forget to do Windows Update too, and do all your Critical Updates, there's a patch for a vulnerability that allows that kind of crap to get on your system. Do it at least once a week....also, see the other spyware/hijackware threads in Tilted Computers, there's a lot of good stuff there.
Also the free virus scanner at
http://housecall.trendmicro.com might find something, give it a shot.