How to change my OpenGL settings

When I want to start the game Medal of Honor I get the following message:
“OpenGL vendor string is NULL”. The game have been starting properly before, but my motherboard was replaced and now I get this. Could someone please tell me where I can change my OpenGL settings? or even better, how to resolve the problem?
please!!!

Forgot:

  • Got windows XP Professional
  • Videocard: Nvidia G-force 4 Ti4200
  • Have downloaded the latest drivers for openGL from Nvidia.com
  • AMD 2000+ procesor (1.7 Ghz)
  • DirectX 8.1b