As you can see, Rockbox provides a simple tool to give your drab old MP3 player stunning new looks and functionality—and I haven't even mentioned that Rockbox can play back virtually any file type you're likely to want to play. Score a big one for free, open-source software. WORKS ON THE iRIVER 5GB
"Rockbox is an open source firmware replacement for a growing number of digital audio players. It has been in development since 2001 and receives new features, tweaks and fixes every day to provide you with the best possible music listening experience. Rockbox aims to be considerably more functional and efficient than your device's stock firmware while remaining easy to use and customizable."