Its funny isn’t it. Using an open graphics standard like OpenGL and things still work differently on different graphics cards!
The game checks for all OpenGL extensions it uses and only enables the ones that are present on the graphics card. Where it seems to fall over is when manufacters have differences that are not covered by the extension specification. e.g. Both cards support the extension but one only allows textures of certains sizes to be used.
I have already found a voodo 3dfx card that I use for testing along with my main geForceII. I am trying to get hold of a cheap Radeon card (7200 or similar) to see why the game won’t work on these cards.
Short answer is I don’t know. Hopefully as I test with more and more cards I will get all of the possibilities covered.