Well, being haunted isn't very likely, but something VERY strange is going on!

Almost every single day, when I'm on the computer I'll just be looking at a site or chatting with my friends on MSN, and suddenly this guy sings, "Save us!" (BTW, I know it's coming from the computer and not from anywhere else, because I always use the headphones.)

It's really starting to freak me out, because I have no clue what could be causing it! (I seriously doubt it's a virus, the computer's running fine.) Any ideas?