[PC Demo] I get sound but no image (black screen)


finally i downloaded the DEMO version.

I have an i5 2500K, asrock p67 Pro3 and a 7970hd with the latest driver.
Windows 10 1703, updated too

My Motherboard doesn’t have the chipset intelHD integrated, so i think the game try to launch it with this instead of my dedicated GPU.
I can’t disable the intel HD since there is no chipset in my motherboard and no option on the windows settings.

And i can’t force the AMD driver to launch the game because the Windows store folder is secured !!

Some help please?