We got into the same problem.
In case you get an error about a missing Datagen.exe during the installation process you can solute that issue by the following steps:
1. Start the installation and wait for the error, abort installation
2. Restart Installation and wait until the installatin process requests CD2 (the datagen.exe should be there at this moment)
3. IMPORTANT: Make the datagen.exe write protected (right click -> properties)
4. proceed Installation
The Installation worked, the game did start, but we were not able to patch it and didnt find a solution for it.