I'm not going to try to answer all your questions but just make a few points (somebody else would be better at answering the others.) If you're only going to dwnld mp3's, then you could also add .jpg & .wmv to your keywd filters. For a start this will reduce those unwanted results that wastes your search bandwidth.

Have Norton set to auto detect (I think it's called auto-protect.) Yes I've never 'heard' of mp3's with virus.