What exactly gives an XP machine the ability to have Direct3D to be enabled/disabled in DirectX 9c? Is it the video card driver? Motherboard driver? Something related to a Windows/.Net Update? A combination of things?
I have a number of computers that don't have the ability to have Direct3D enabled or disabled in DXDiag and a small number that can. The computers are all part of a lab and have very similar setups (I can't say they're 100% the same, but really close). I think I can fix things if I know what gives an XP machine the ability to use Direct3D.