LOL, aren't we all. Maybe if I have some free time later, I'll try uninstalling/reinstalling CoreAVC & NEO HD.

BTW, I don't see why people think Windows 7 is going to be such a big improvement.

I've tried the ffd approach but it didn't work, still no sound.

I'm a total video noob but here is what (seems) to work for me...

After de-installing Cineform and re-installing it gave a message that no valic AC3 decoder was found and suggested I installed ac3filter from AC3Filter
After I installed ac3filter I have sound :)

There's a new version of the CoreAVC (1.9.0) h.264 decoder, which will take advantage of nVidia's CUDA GPU programming framework. You need to have an nVidia graphics card, of recent vintage and have a CUDA-aware Windows video driver of at least version 181.69. The most recent beta driver (182.05) works fine (Just tried it).

<simplified explanation alert> What CUDA does, is it uses your GPU cores as mini-CPUs, to do calculations, in addition to providing the raw video to your display. Think of it this way. In a "normal" computer setup, the CPU would have the responsibility of the math to create a wire frame of a 3D object and the GPU would handle coloring it in. In the case of a decoder, normally the CPU would spend it's time turning the file's contents into pixels and the GPU would just worry about painting the pixels on the screen. CUDA allows the graphics card to "help" the CPU with the decoding.

There's also a new version (1.1.1) of the CUDA-based h.264 encoder, BadaBoom:

Products | badaboomit.com

The trial is full-featured and expires after 30 encodes.

I've been playing 5DII and AVCHD clips all night with CoreAVC 1.9.0 with Windows Media Player. Really smooth, and the CPU is doing very little, it's all in the GPU - very nice. Now I have to try Badaboom.