Everybody knows that the Xbox 360 120GB HDD add-on is a total rip-off. I mean, come on Microsoft, who are you trying to fool here? $180 for a 120GB drive? What is this, 2002? Give me a break.
Well, you don't need to bend over and let Microsoft have its way with you if you don't mind spending a little time doing it yourself. A resourceful modder who goes by "TheSpecialist" has come up with a way to get a specific model of Western Digital 120GB SATA HDD (which you can pick up for $80) playing nice with your Xbox 360. Sure, it won't click nicely in place on top of your Xbox, and you can't transfer your old saves over, but you'll get the satisfaction of knowing that you didn't confirm Microsoft's assumption that they can charge whatever they damn well please and people will pay for it.
TheSpecialist's HDDHackr v0.90 - Adds Support for 120GB Drives! [Xbox Scene]