My guess would be your video card does not meet the system requirments
here they are
- Operating System: Windows® XP (with Service Pack 3) and DirectX® 9.0c or (Windows Vista® with Service Pack 2)
- Video Card: 256 MB 3D hardware accelerator card required - 100% DirectX® 9.0c with Shader Model 3 support*
- Processor: Pentium(R) Intel Core® 2 Duo 2.6 GHz or AMD Athlon 64 X2 3800+ or better
- RAM: 1 GB of RAM for Windows ® XP / 2 GB Windows ® Vista systems
- Hard Drive Space: 8 GB of uncompressed hard disk space (Plus 500MB for swap file.)
- Sound Card: DirectX 9.0 –compliant sound card
- DVD-ROM: DVD-ROM
- Peripheral:100% Windows(R) XP/Vista - compatible mouse, keyboard and drivers, 100% Windows(R) XP/Vista - compatible 4X DVD-ROM drive or better (600K/sec sustained transfer rate) and drivers
*Supported Chipsets for Windows(R) XP and Vista
All NVIDIA® GeForce™ 7800 256 MB and better chipsets
All ATI® Radeon™ X1800 256 MB and better chipsets