Why won't my mp3 player turn on?

what do i do if my mp3 wont turn on i need help asap and if i plug it into the laptop it says device not detected

SaMe ThInG fOr Me BuT wHeN mY mP3 pLaYeR wiIl WoRk In ThE cOmPuTeR (pLaY mUsIc) BuT wHeN i UnPlUg It, iT dOsN't wOrK,, :(((