No, there isn't any file you can search for to modify or delete. Spyware programs and the like name their files cryptic things and put them in places you wouldn't think of. That's why you download spy/adware killers and they them remove that stuff for you, as they know where all of the files are.

Also, if you know that you weren't the one on the computer and don't want to get busted by your parents, why don't you tell them what it was doing when you signed on? It's better to tell them before-hand, because if you wait until after they find out it looks like you're hiding something.