You need to install the crack (it says so in this very page, but I won't blame you, 99% of the games here don't require you to do this).
In order to do so, go to the CD (the one you mounted to install the game), there's a folder called CODEX there, copy the contents and paste them wherever you installed the game. It will ask if you want to overwrite some files, click yes to all. That will make the game work.