My friend just got me Star Wars Galactic Battlegrounds Clone Campaigns (the expansion pack) for PC. I've been playing his original version, so Star Wars Galactic Battlegrounds, as required, was already installed. We installed the expansion pack, but when we tried to start up a single-player game, we got an error message which stated, "You must insert a game CD to play a single-player game, and then restart Star Wars Galactic Battlegrounds."

This didn't make any sense. We had the CD in the disk-drive. Well then, my friend went home and attempted to play the same game off my expansion pack disk. It worked, supposedly eliminating the possibility that the CD itself was the problem.

So my question, as most have probably inferred, is, "Does anyone know of a possible reason for this, or can anyone provide a solution that has worked for them?"

For clarification, I'm running Windows XP.

Any help or ideas at all are appreciated.