Hmmm, Demo runs fine under Windows 2000. Considering that it uses the Unreal engine then Compatibility mode is not necessary. Since as far as I know there are no compatibility problems with the Unreal engine and NT os's. Exactly what error do you get with the game without running in compatibility mode?
It's likely a corrupt install, The game is not updated, your drivers not installed, or a misconfigured config in the game.