How do you Start oblivion game with no disk

use a no disk crack for the PC version, although this is illegal if you intend to avoid using the disk because you are borrowing it from a friend or if you obtained it illegally. but if you own the original its perfectly fine to download a crack (in most countries), although to be honest the game doesn't load from the disk on the PC version so i don't see why you would'NT just put the disk in.