I downloaded the civ5 demo from steam, and after 3 hours of waiting, I started up the game. The intro movie looked impressive enough, but as soon as I got into the game, even the menus, the resolution was low and when you start the game everything is choppy and slow. I know my computer could easily handle this game - I've got an i7 processor and 6 gigs of ram; so why is the performance so bad? Is it because it is the demo?