Do you have a Jtag Xbox ? or a Flashed DVD drive in a STD Xbox ?
If you have a Jtag you will need to use a program like Xbox Image Browser to extract the ISO to your PC
Then put it on the HDD in a Folder using explorer, and open it with a program like XEXmenu
If you dont have a Jtag then you can only rip the DVD to the hard drive in the normal fashion through the XBOX menu, but you will always need the disk to play the game
I have never attempted the second solution as i have a jtag and a Std Xbox too and only use the Std online