OK I have XP set to quadraphonic, and Power DVD set to SPDIF, I get no sound from rears.
When I set Power DVD to 2 speakers, I have sound from all 4. But I also have options to choose:
A3D/DirectSound3D
Dolby Surround Compatible
Stereo
TruSurroundXT
Dolby Headphone
Which one do I choose? There's also an advanced button where I can change the settings for the above mentioned 2 speaker mode selections.