This is where I found out how to download and copy xbox 360 games too. It's pretty easy to do.
You need to learn how to flash your XBOX 360. This site showed me how with really clear tutorials.
Here are some important details about the site again:
-Must burn to DVD+R DL discs which are around 8.5GB
-You stealth patch your games so you cannot be detected on Live
-the fee isn't monthly, it is one time
-you must FLASH your XBOX drive, NO mod chips - the site shows you how.
-you can still get achievements
-and you can still play your old games
You'll learn how to legally copy your XBOX 360 games for backup purposes and also to download xbox 360 games.
So go check it out for yourself, I hope you enjoy it!