Full OpenGL support on consumer-level drivers is a fairly new phenomenon. Early 'OpenGL' drivers really just supported a few basic commands to get specially-written games (like Quake, Quake 2, others I forget) working.
You can try Googling for 'nvidia driver opengl 1.2 support' and the like.. or 1.1... those were the first versions of OpenGL that I remember video drivers fully supporting. Then get the latest drivers that still support the 7600 and Pentium 3s. I don't know how old the 7600 is but Nvidia probably stopped officially supporting P3s a while ago.
Windows 7 vs XP shouldn't matter, but then, in this case, who knows.. this is the type of thing I doubt Nvidia would test for in their latest drivers.
You could try setting the 'Compatibility mode' in the game's properties to XP or whatever else, it might work.
And as I remember, XP Professional supported multiple physical CPUs but Home didn't.. as far as 7, I don't know