Another possibility I have heard is an executable virus that has been renamed to look like an mp3 file... but it would be up to the media playing software to look at a file and figure out if its an mp3 file and if its not if its an executable and try to execute it... not many programs do this, I tried for example renaming an executable to mp3 and winamp didnt do it, tried renaming it to avi and windows media player said it was not an avi. So it seems in most cases an mp3 is safe...