Ok my friends...I've been trying to find all the info I can get on this and I'm hearing different responses.  So I figure I'm just going to post my problem and see what kind of answers I get.  So here it is.
 
I have a MSI Diamond motherboard with built in Soundblaster X-Fi Extreme Audio HD sound card on it.  It has a SPDIF output that I have connected to my Home A/V unit.  It is a Sony DE945 Receiver.  I have a optical cable running from the sound card to the A/V unit.  I'm running Windows Vista Ultimate.  When I go into my sound settings I see the option for SPDIF.  I change it to that and run the tests.  DTS, Dolby Pro Logic, and so forth.  When I run the DTS test the blue light comes on for my receiver and it says 3/2 DTS.  Everything sounds fine.  Same for Dolby Pro Logic.  I also run test for 24, 48, 96 PCM.  All run fine.  Now....whenever I try to play anything....MP3...Blu-ray...DVD etc... I only get 2 channels. and it says 96 PCM.  I check all the settings in the applications I run and everything looks fine.  I also installed AC3 Filter thinking that this might fix my problem and still only 2 channel.  I wouldn't even mind 2.1 so my sub is getting used but no...nothing.
 
What am I doing wrong?  Any suggestions would be great.
 
Wares

unless you have a sound card or chip that support dolby digital live on the fly encoding then you can only output stereo signal through a digital output.
 
  creative does not pay for a dolby licence so can only out put surround sound through discrete analogue channels.

Thanks for the info bud...not what I wanted to hear though.