The original XBox was an abortion of trusted computing and DRM. Supposedly in order to maintain a level playing field for XBox-Live (but really just because they're assholes), Microsoft used the concept of security-thru-obscurity. The normal BIOS was in a flash chip, just like you might expect. But when you dike out this chip to hack the XBox, a secondary BIOS kicks in, making your hack completely worthless. In fact, it turns out that the original Flash BIOS was a decoy, designed to trick you. After months of research and investigation, an MIT electrical engineer figured out where the real BIOS was. It was hidden inside the NVidia GPU. Once he figured out what board tracings the BIOS used, hacking the XBox became a trivial matter of soldering.
Microsoft was pretty upset about this, and so they released a new XBox, the so-called second gen. Thanks to help from hardware hackers around the world, the second gen was cracked in 3 days.
There's actually a book that explains the whole story, written by the engineer who discovered the scam. He also gives instructions for modding your XBox, and advice on buying electronics tools. Even if you don't own an XBox, it's a damn interesting book.
http://www.amazon.com/gp/product/1593270291/sr=8-1/qid=1140217177/ref=pd_bbs_1/102-5244716-7442530?%5Fencoding=UTF8
