unbranded 8Gb mp3/4 player disk error n not working,plese help?

my unbranded 8Gb mp3/4 player has disk error n not working,.Can any 1 help repair this bearing in mind the following :i was given this by a friend and do not have any manual or disks for it or anything else xcept headphones with it.I think i pressed the firmware update by accicdent in the settings menu which is still accesible as well the fm radio's working.but it does not initialise, instead it just goes on to the menu n ive lost all my music files.If so are the files retreiveableand if so how