There seems to be a common problem with these players.
I've just been trying to fix one for my mate.
It wouldn't recognise or play any of the wma / mp3 files. Even though they were clearly visible when browsing as a removable disk in windows explorer.
I managed to get it going by Re-formatting as a removable drive (using windows 2000 Server) it wouldn't work properly on win2000pro, XP home, or XP Pro ! ! !
I'll try to upload a zip containing all the files on the OEM CD that we have.