It's not rocket science, but it's not as straightforward. Abrown15 has it pretty much right.
On a PS2 you just copy the disc. Easy as pie. You need a MOD chip or some other method of tricking the system into booting a copy, but the actual copy is absurdly easy to make.
On the XBox, however, the disc is encrypted. AFAIK, no decryption software exists for the PC. So yes, you rig up a little mini-network, boot a custom disc on the XBox and get it to rip the DVD and send it over the network to the PC for burning.
The XBox will then boot the unencrypted copy as well.