If I change the renderer to OpenGL, close then reload GLZDoom, I get a mostly black screen with the top left quarter of the game showing in the bottom-right quarter of the screen. Nothing happens though, it's just a black window. I think it works on my "proper" games PC (which has an 8800GTS, no problem there

), but I couldn't really care less, to be honest; I just cannot stand playing Doom with 3D acceleration.
And before anyone jumps on
that angle, it's nothing to do with Graf's sterling work on the engine, the same applies to any other accelerated 3D Doom port.
UTNT looks sumptuous in software (bridge "bug" excepting), so I'm happy.