Ok look. For those of you who are downloading torrents (I know you are, don't lie), there is a chance that the game is corrupt. Let me explain the "Dirty Disk" error:
When the person that copies the game to his xbox has a dirty disk, the files are obviously not going to copy right. The xbox doesn't know wether your loading it off of a disk or not, so when it try to load a certain file and it can't do so successfully, it gives that error, because the game assumes the disk is dirty (If anyone has a damaged disk already they should be slapped). So what you need to do is Either make sure your disk is clean or your dvd drive is clean and for those of you downloading torrents, your basically playing a game of Risk, because the person who copied it may have a corrupt copy, but thankfully for you little pirates, most people are kind and don't seed bum copies of games.
This should be the final word on the dirty disk eror. No, there is no top secret anti-backup software genetically encoded onto the disk, it's just the disk itself or your xbox. And for those of you who are saying the game won't run right while it is copied onto a DVD-R, though it is a DVD, it reads slightly different, a little more sensitive to be honest. Make sure both DVD's are clean when you copy. Also, if your trying to run the game on a burned DVD and Un-Modded Xbox, your wasting your time because you will ALWAYS get the Dirty Disk error. It's called a Media Flag. Research them and you may be able to correct your problem.
Cathesdus