I bought a modded 360, with what i was told is an "extreme mod". It came with several backed up games, so I know it works. I already wasted 6 verbatim dvd+r dl disks trying to get a game I got to work. I use abgx360 to check the game, and burn it with ImgBurn at 2.4x.
I even did everything in this tutorial
http://www.bimmerpost.com/forums/sho...d.php?t=464000
anyway, the xbox reads all my efforts as a dvd movie file. It reads the games I bought with it just fine