http://www.xbox-scene.com has everything you could ever want to know about Xbox modding and such. this is where i got all my info from.
on my xbox, i have a 120 gig hard drive. on this, i have 37 games, emulators and every single rom ever made for MAME(arcade), NES, SNES, Genesis, N64, Atari, and Lynx. yes, my friends, my xbox kicks ass. oh, and since i ran out of room on my hard drive, i've burned around 40 DVD, each with anywhere from 1-4 full games. WOO!
oh, and all the info you need to do this kind of crap is on the website i linked to.