Can't enable Direct3D acceleration.

Hello,

I can't seem to enable Direct3D acceleration. I don't know what happened
but all of a sudden I can't run any of my games. When I try to run Unreal
Tournament 2004 I get the message:

"Please enable Direct3D acceleration. You can do this by starting dxdiag
and enabling Direct3D Aceleration in the Display 1/2 tab after installing
DirectX 8.1b (or later) and the latest drivers for you graphics card."

None of my other games will work eithere.When I open dxdiag and go to the
Display tab, under DirectX Features Direct3D Acceleration says "Not
Available" along with DirectDraw and AGP Texture Acceleration. All are
unavailable.

I have DirectX 9.0c installed and an ATI Radeon 9600XT 256 video
card.

I've tried reinstalling the video drivers and DirectX too. I've also
noticed that 2d accleration must be suffering too since everything takes
much longer to redraw on my Windows XP desktop.

Ideas?

Thanks,

Jeff