When a game comes on 2 discs, the first disc is usually the disc required for running the game. Try inserting Disc 1. If that doesn't work, insert Disc 2.
Is it a genuine version of the game or is it a pirated/ free copy?
Good answer. This is a no brainer with legit software.
If pirated, the needed DRM sectors are missing. If that is the case, this discussion should be closed.