Halo CE problems with 32bit directx/directdraw on 64bit win 7

I am trying to run my old copy of Halo CE on windows 7, but whenever I try and run it, I get the error:
"A problem occurred initializing DirectDraw. Hardware acceleration maybe disabled, please run DXDIAG"

I run the 32bit DxDiag, and it says DirectDraw acceleration is disabled, and direct3D acceleration is only partially enabled, but when I run the 64bit DxDiag, it says these are both enabled. I assume the problem with Halo is that it is a 32bit program, but I have no idea how to solve the problem, or exactly what it is. My video drivers are up to date, I have tried updating DirectX, and installing older versions (several of which it won't let me, because it says it has a newer version isntalled), I tried compatibility mode for xp, 98, and 95, and running as an administrator, and I have searched through Catalyst Control Center for some kind of directdraw options or something, and found nothing.

Any suggestions?

Thanks,
Tom