Could you really not use OpenGL under Windows 95? I seem to recall running GLQuake and GLQuakeWorld a good while before the release of Windows 98. GLQuake was released in 97.
I am pretty sure glquake used a weird system of drivers called mini-gl that were either provided by ID or graphics card makers. They only supported an extremely limited subset of opengl. See: http://en.wikipedia.org/wiki/MiniGL
