Well, trying reinstall wont hurt. Also check that your DirectX is up to date.
If it works you should see the pixel and vertex shader versions supported by your GPU in the bottom of the launcher:
(game requires pixel shader 2.0)
If none of this works I fear that you might be out of luck and I'd recommend you switch to Windows 7 since thats where your hardware support is. But that is a choice you must make.