A recent Computer mag article suggested that this level of PC built from your excess components can be used to make a CD-self-booting MP3 player that runs on a modern version of DOS - and thus works acceptably for the level of hardware involved - doesn't even need a hard drive! - just add some speakers or headphones. (8X Cd player)

You can also use it to boot a Linux standalone firewall (needs a HD though) - you just add a few network cards - don't need extensive other gadgets - not even a KB & Monitor - for once setup you adjust it thru your web browser via the network...