Try zdnet and their product called SpyBot. You can demo it for a month I think and then have to buy it. It does a good job of catching spyware as long as you keep it updated. Also make sure you have a good virus protection program (Norton,erc.) and keep it updated and you should be fine.
Spybot isn't a ZDNet product, nor does it expire after a trial--it's 100% free.