GeeXboX is a full operating system, running under Linux and based on the excellent MPlayer. No need of hard drive, you just have to put the GeeXboX bootable CD into the CD-Drive of any pentium-class computer to boot it. Moreover, GeeXboX is a free software, created thanks to many open-source software. This means that everyone can modify it and build his own release of the GeeXboX. You may wonder why you could have to boot on another operating system to play your media files, but just think about the Mini-ITX plateforms like VIA Epia/Eden or Shuttle barebones. It's now affordable to bring DivX to your home cinema, plugging this kind of computers directly to your TV. At the time of the first development release (December 2002), it was only able to play DivX movies, but for now, nearly every kind of media files can be played from GeeXboX.