My computer says I don't have the Empire At War disk inserted when I do. Whats wrong?

I just bought the Empire At War Gold Pack and have installed and uninstalled now installed again. When I go to run the game I get an error message that says to insert the original game CD but it is in the drive already. I don't know what to do. The box says retry and cancel but no matter how many times I click retry it just loops. Anybody know how to fix this?