Haven't seen this problem... help?

Hi, I was hoping some of you smrt people could help me out.
OpenGL games recently stopped running on my system.
I have an AthlonXP 2400+, with 512 RAM and a GeForce4 TI4600.
DirectX games work perfectly, I can run Halo and Splinter Cell perfectly fine, but Quake 3 and Jedi Academy load even the intro movies like a slide show.
I was running leaked Detonators (51.75) but have since gone back to the older drivers (45.23) but nothing has changed. I tried deleting the OpenGL .dlls and unless I missed one, it had no effect.
Anyone know why this might have happened? I’m almost certain it started before I updated to the beta drivers, but I can’t say for sure.