Go to this site and run their scan, it'll do about everything you'll need. Also, whoever uses your PC, tell them to stay off the porn sites - that'll get you every time.
If you don't know what you're doing, stay away from Hijack-This as you can turn some stuff off on your PC, which will disable things, and then you're totally screwed because you didn't knwo what you were doing in the first place.
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