One day my DirectDraw hardware acceleration stopped working. I couldn't watch DVDs and videos would run really slowly if I scaled them. (DxDiag said that hardware acceleration was "not available" for DirectDraw). Re-installing DirectX 8.1 or my video card drivers didn't fix it. When I even got a new video card and it was still disabled, I decided I should look around and try to fix it.
It took me a long time to find this bizarre trick, and I didn't believe it would actually work, but it did.
Windows 2000 comes with netmeeting. (In Accessories... Communication). Run this. In the options menu, select remote desktop sharing and follow the wizard through, as if you are installing it. After it's started, go to the same option and disable remote desktop sharing. I did this (this was seriously my last ditch effort), and lo and behold, it worked! DXDIAG should now show hardware acceleration being enabled.
Keywords: DirectDraw, DirectX, 8.0, 8.1, nvidia, geforce, windows 2000, win 2k, dxdiag, slow, registry, PowerDVD