There is a free adware scanner called AdAware from Lavasoft, its not THE best (I know Spyware Doctor was at some point not sure if thats still true but I don't recommend it anymore) its been more than adequate for my purposes however, so either go find a commercial one or get AdAware (which can also be commercial if you pay for it - gives you realtime protection whereas the free one doesn't, just scanning/removal)