help with backing up my original copy of warcraft 3

[krazywood]

I bought a legitimate copy of warcraft 3 today and i tried backing it up with no results. It says put in the warcraft 3 cd when i try loading the game with the burned copy. I need help or tips to get a backup working cause my brother and i both want to play the single player game at the same time on our seperate computers. any help on this matter would be greatly appreciated.