If you’ve got an old junky XBox around, and would like to put something, well, *useful* on it, like XBMC, then I’ve got a great link for you which allows soft modding without having a copy of any of the exploitable games.
Patched xboxhdm 1.9 with exploits will allow you to boot another PC while hotswapping your XBox hard drive into that machine. It has all of the known exploits on it, I believe, so you don’t have to have your XBox connected to another machine or anything, nice and simple. After that, use a fully automated installer like Auto Installer Deluxe to do everything else for you.
So, don’t throw that XBox out, make it into something much better.