Read everything first...
1) Get this:
http://www.nvidia.com/page/nvdvd_downloadtrial.html
2) People seem to claim that WinDVD 6 is better for DVD playback but its 50 US dollars. Screw that eh!
3) Where can I disable S/PDIF?
Browse to the NVIDIA DVD Decoder Properties and select the “Audio” properties page. Click on the “Speaker Setup” button and select “a receiver” and then check “via an S/PDIF cable”.
4) I have found this lot. It's not directly a procedure, but once you understand it all, you'll probably figure out what settings to activate or not in the options/properties page...whatever its called
Interlaced content displays a video image as two separate fields. The first field displays every other line of the image and the second field is displayed at a slightly later time complete the image. This matches the way conventional televisions work.
DVDs created from content that was originally viewed on television will likely be interlaced, such as music videos or concerts. VCRs and many camcorders record in an interlaced format since the video is intended to be watched at a later time on a TV.
De-interlacing is the process of taking two interlaced fields and generating a single frame to be viewed on a progressive display, such as a computer monitor.
Bob is a de-interlacing algorithm that displays each field of an interlaced image separately. The missing lines for each field are interpolated from the lines that are present. This is the de-interlace mode used when "display fields separately" is set in the NVDVD Video property page.
Adaptive de-interlacing is a more advanced algorithm that looks at a sequence of frames to determine if an area is still or in motion. For pixels that are still, the fields are simply combined without a blend. If in motion, the fields are blended together. This produces the best visual results but is more computationally intensive.
NVDVD is able to perform adaptive de-interlacing in hardware, which keeps the CPU from performing this intensive task. This maintains smooth DVD playback even when de-interlacing.
5) Switch to the default audio renderer.
Good luck.