if i get a premodded xbox from modchipman.com with a 120 GB HD and the Alladin Advance 64+ will it be possibe for me to copy the original game to the hd without messing with the system.
Very good. Just connect to ur xbox and transfer a downloaded version of Boxplorer to your e:\apps folder, and learn to use Boxplorer. I think thats the easiest way of backing up games to ur HD.
Make a CD-RW or you can FTP if you know how to, then get a program called DVD2XBOX, the easiest/best program for backing up games. No you won't have to mess with anything inside the box.