I realise this topic is somewhat dead but Oatrick's idea will not work without getting the MP3 player OS back onto the device, formatting it will make is a blank memory stick and it wont know how to read .mp3 files, wont have any menus or any content.
Dont format the MP3 player without backing up all files (including hidden files) and finding an updated OS online to put back on the device. I cant guarantee this will work but it's probably got the best chance of success.
Teris
April 2010