my openGL isn't working, can I reinstall it?

Sorry, but I don’t really understand quite well what OpenGL is. All I know is I’m having trouble with most games (Counter strike says that video mode is not supportes, Medal of honor says my OpenGL doesn’t work).
I had it working ok before I formatted my whole HDD and reinstalled everything. So is there any way to reinstall OpenGL?
I’ve been reading other posts and downloaded glinfo. This is what I get:
Driver version Unknown
Vendor Microsoft Corporation
Renderer GDI Generic
OpenGL version 1.1.0

Extensions GL_EXT_bgra

You can contact me at (e-mail and MSN or Ymsn)

Thanks a lot.

The drivers that come with XP dont support OpenGL. You have to find out what kind of 3d card you have and install the drivers from this manufacturer (if they have XP drivers which support OpenGL that means).