Annihilator 2 (GeForce GTS) & Windows 2000

Annihilator 2 supports OpenGL?
My diagnostics software shows “OpenGL not supported by display adapter”
Why?
My OS is Windows 2000

You don’t have proper drivers installed. Go to nVidia and download their drivers for your platform.

Yes. In particular, try this:
http://www.nvidia.com/products.nsf/htmlmedia/detonator3.html