Sometimes Mp3 players come with special software (not drivers) that copy the songs for you. Did yours come with something like "MusicMatch Jukebox", or something of that sort? If so, try using that software to load your songs.
This software usually, before copying the files to the mp3 player, encrypts the media in order to prevent you from copying the songs onto another machine.
I've found a way around this for certain players; convert the mp3's to .wmv/wma files before copying them to the device. For some reason these manufactures don't care if you distribute wmv/wma files to other machines.
