Just grabbed this from Steam. Enabling UseGLSL got me past the hardware requirements screen, and the game launched fine. The opening movies played properly and the menus work fine. It even draws the characters and seems to play acceptably, but I can't see any walls or floors at all.
Since this is Prince of Persia, that's not very good. I've fiddled with the registry a bit to no avail, anyone have any suggestions?