Games can install from copied CD but can't run on it..

[cutepaul]

Help me I'm a newbie. I used Nero to make an ISO. The ISO successfully burns to a CD and the game is able to install properly with the copied CD. The problem is that the game can't start with the copied CD is in the drive, but can start when the original CD is in the drive. Strange sh*t and it's pissin me off man. Do they put something into the game that makes it recognise that a copied CD is trying to start it?