Spybot
Ad-aware
Those are two of the free options to rid you of your spyware headaches. There are better, more thorough options available that cost money. The best is Giant Software's utility. However Microsoft purchased it from Giant and has repackaged it which is available in beta format
here. I don't know what Microsofts plan is in terms of charges for the product. But it is widely rated higher than any other option. If you are uneasy running beta software, the two options at the top are viable alternatives (I run both). Just make sure you regularly update them, and regularly scan.