Thanks for your answer.
We executed dxsetup.exe but then a window pops and all choices are "grey", we can't click on anything. We also made sure both cards got the latest drivers.
If I understand correctly your answers in this topic http://en.modding-union.com/index.php/topic,31635.0.html
, the game tries to start with the Intel card (which got the bugged driver) although it is desactivated. Therefore we need to change priorities between the two video cards, right? Do you know how to do it? I've seen some suggestions about going in the BIOS, but I'm not too confident about that.