@ David R
Yeh, I don't actually think its Open_GL, but it definately isn't right whatever it is.
Examples of what do and don't work:
* Half life installed from CD will work properly (but crashes for a different reason)
* Half life on steam from a previous installation of windows (just coppied from my last format) will be all slow and smooth
* Games like CoD, CoD4, any of the Source games (anything normal) it works fine on
* GTA SA menu has the slow smooth mouse, but as soon as you start the 3D part of the game, then come back to the menu, it's fine.
The only way to get Half life (Opposing force and Blue shift) on steam working is to run them in software mode.
@ GamerDude
Yeh you've already told us what it does wrong - have you tried any of the techniques I told you to rule out whether it's a virus or your computer that's doing it?