Your PC nor your DVD burner will not read XboX games. To backup originals you will need to FTP into your XboX via networking to your PC, basicly letting your XboX read the Disc while your PC copies what it reads.
What you need...
1) NIC on your Computer
2) Ethernet Cable
3) ISO Burning software (Nero and DVD Decrypter most popular)
4) XboX ISO extracter/reader (such as Qwix, Craxion, IsoMaker 2.0, XDFS REader, etc..)
5) FTP software (FlashFXP, Cute FTP, etc..)
I could get into step by step on what/how to do, but there are way better tutorials on this subject (easy to follow and understand). Here is a direct link to everything you need, from setting up your Network, configuring your Network with your XboX, ripping, burning, etc. Do it once or twice and it'll be like a sixth sense.
BR7: I read the tutorial and I have one question. After the process finishes, I'm left with an .ISO. Can I burn this to a DVD-R and play it in my xbox without modding?
I understand everything that was said I have a moded xbox and I know how to take the files from the xbox to my pc and use quix to create an iso but I want to burn that iso to a dvd and give it to a friend so he can play the game I did it using a -R and it won't work for him I'm trying to figure out how can I get an iso image backup to work on a UNMODED xbox
One thing that I would just like to specify is that if your going through a hub or router (try using a hub first routers are fun if you don't know how to ftp using the ip and DG) you need to use a Standard or straight through Cat5 or RJ45 (same thing) but if your doing a direct connection from your computer to your xbox then you need a crossover Cat5 or RJ45. (can be found in most places like circuit city and even eb games or gamestop).
And like dossie said as of right now no un-modded xbox can play burned xbox games, and you can't get into your xbox without file transfer protocal set up on your xbox (or ftp is on your xbox lol)