pca,
I note you have been able to run the OpenGL version of Q2, have you tried the OpenGL version of Hexen II? I can run the normal version of Hexen II on XP Pro, but not the OpenGL version. I am running a TI 4800 with 42.30 drivers. I haven't tried Q2 yet. Are there any known problems running OpenGL under XP Pro, or with the above drivers?

Hexen II is a good game isn't it? You may also like the original Heretic which is pretty basic graphics but good gameplay. Heretic is also available on the web as an OpenGL version here