NO, it's not an illeagal version. If any of you remember, this error was common when MOH:AA first released. Unfortuneatly, doing a search here I couldn't find any of the old topics on it. You may want to ask Rudedog, or try searching PMOH.com
RodR brang up a good point, try putting the 1st CD back in again. I think that was the solution, too.
Hognose, it is most likely your CD drive. Possible that it is no good. When I tried to install MOH from my old drive it couldn't find the 2nd CD. Bought a new drive and all was well. Good luck.