Have you changed drive letters since original install? Activision maintains the installed source drive letter in the registry, and its possible that could cause such an error, though I have not tested (by removing/changing drives after install) myself. And Cheesewiz is right; you only need CD1, wich is the one with the copy protection. If you are using a copied disk, or non-original disk, you can get this error. And if you are using a virtual disk, you can get this error.
Good hunting...