Make sure that the latest drivers of your graphics card are installed and that you at least 512 MB of video memory.
To update the drivers of your graphics card: http://www.wikihow.com/Update-Your-Video-Card-Drivers-on-Windows-7
We recommend that you use a graphics card with at least 1 GB of video memory and support for OpenGL 3.0 (Shader Model 4.0).
AMD/ATI: Radeon4 xxx or later.
NVIDIA: GeForce 2xxx or later, Quadro FX 3800 or later.
Intel: HD 4000 or higher.
Caution: Older computers with limited performance may not be able to run the game!