FTP - File Transfer Protocol.
So what to do:
1.Boot you xbox with chip on and note the IP adress on your xbox according to the dashboard.
2.Start FlashFXP or any other good FTP application. Connect to the xbox using the IP and mostly user: xbox, password: xbox.
3.Transfer all files from D: (the xbox dvd game thats inserted atm). NOTE Game can NOT be running. You must be in the dashboard. Transfer the file onto your PC HDD.
4.Download an application called Qwix and read the instructions with it. It will tell you how to create an imagefile from the transferred files
5.Burn the imagefile with any burning application, I would recommend using ImgBurn.
6.play and enjoy your backup...
For several guides in the matter that contains a little more information and generals tips please take a look here:
http://forums.xbox-scene.com/index.php?showtopic=107130