Umm, it's been a while, you'd probably better off checking the old xbox forum on xbox-scene. It's been a while since I messed with any of that stuff. Xbox is good for old school emulators, and Xbox Media Center (homebrew app) was fantastic for its time, but the system simply isn't powerful enough to handle HD content. Blu ray is definitely a no go on the original xbox.
The key word you are probably looking for is 'softmod'. I think it's relatively simple provided you have the correct game. And you might need to have a way of getting files onto an xbox memory card. Like I said, it's been a while. I used an actual modchip which involved some soldering work