A crafty Japanese DIYer has crammed an entire PC into the shell of an old Game Boy system. The computer is fully-functional (assuming Windows XP is "functional") but lacks a built-in screen and a few other niceties of modern computing. Not practical by any means, but since when does geek hackery have to be practical?
Other features of the Game Boy XP PC include:
Runs Windows XP off of a 4GB compact lash card that slides into the game slot