My ears are telling me it's from the Jnr Walker tune. EDIT: Heh, it could well be from the Prince tune! I just sampled his scream and if you pitch the tail end of his scream up by about a semitone, it sounds pretty close to what they used in Jump Around. The Jnr Walker sample (on the youtube clip) isn't clean, like the Prince sample is, as it has a snare drum mixed in with it. Unless the original vinyl has hard panned left and right stereo sound, it may be clean too. I'm undecided now!