Video of a very well done case mod. The Mac OS Xbox (YouTube link).

The music however, sucks. Sucks bad. Engadget quoted the video's author saying there's about $1500 worth of hardware in this case, which he claims (so incorrectly) is equivalent to $4500 Mac Pro (maybe in his wet dreams). That's like saying a Hyundai is the same as a BMW because you can put premium gas in it and drive it on the same road.

Using a single Core2Quad processor, 2.5" drives and shite Ballistix memory.

But, again, the mod work and the video are really great.