OpenGL problems with 9600Pro

Over a month ago my son tried to install a demo which I believe was as
OpenGL demo game. Since then, and I was using current Cats at the time, I
have lost OpenGL. Every OpenGL game I have, now gives the same error "cannot
open OpenGL subsystem" or something to that effect. Or, the game just
doesn't start.

I am now using 3.8s. It and no version in the past month or so have worked.
I have tried all the so-called "fixes" (editing win.ini, replacing the
opengl32.dll file etc.) in the OpenGL forums but nothing works.

So, am now faced with the prospect of reinstalling WinXP since, I believe, a
fresh reinstall would correct the possible Windows system files that have
somehow become corrupted.

However, could I repair the Windows XP installation using Recovery Console
and would this avoid having to reinstall everything?

Unless anyone out there has any ideas?

Ron