If you are running a ATI Graphics card and you play HL1 games (CS, Day of Defeat, ect...) here is a fix for not being able to play in OpenGL mode.
This is for 64 bit driver. OpenGL in Windows 7 with legacy ATI Geforce x1900 GT :: Vertical Visions
I have tested this with my Radeon X1650XT and it is working perfectly in DOD and CS
It is pretty basic but if anyone needs help with this let me know.