I've always prided myself on keeping up with technology, but could someone pls give me (or point me to) the basics on MP3 players? I purchased one for my son (iRiver, I think) and while he can tranfer tracks from CDs to the player, I have been mystified about where to purchase MP3-format tracks on-line. Every time I try to help him download something it seems to land in the wrong format. Any and all advice is greatly appreciated!