CDkeys are not linked to the cd itself. There is a batch of code inside an installation program to figure out if a cd key is valid or fake and you could even trade your key with a friend and use a different key to install.

As much as I hate the idea of Cdkeys, I think having to have the cd in the computer to play the game is complete BS and more of a pain in the a$$ than anything else. If you just make a batch code where no two cdkeys can be connected to the internet at the same time (LIKE QUAKE4) you shouldn't have to make people have the cd in the tray. In fact, I love PC gaming over consoles for so many reasons but at first, it was to get rid of having to have that damn cd in the computer to begin with. This way, if someone REALLY REALLY has to play a pirated game, they have to disconnect their computer from the internet to do so, AND DURING THIS TIME THEY CANNOT DOWNLOAD ANYTHING ELSE PIRATED. A nocd crack is a VERY VERY easy way of getting around that No CD present B.S.