HI I have the same problem but in XP when I was watching movie or listening to music, it was playing thru all the speakers (5.1)not true 5.1 . But in Win 7 only the front 2 speakers (Stereo 2.1).
It is Right that in Win 7 it plays thru the front speakers (Stereo 2.1) WHY Because mp3`s are only Stereo 2.1 and about all 700MB movies.
True 5.1 is for 5 channels Front 2 ,Rear 2 and Front Center . The Movie or Music HAS to HAVE IT
and to enable the matrix is BS it sounds like CRAP (ticking the room option) Solution:
On Windows 7 I Listen to music and watch movies on Media player Classic. WHY because it Can enable the channels I need, this is the only player that I could fine that can do this.
Here is what to do in it to Get sound thru all 5 speakers NOT TRUE 5.1 Sound also works with more speakers All the same sound thru all the speakers and doesn`t sound like Crap
a 5.1 Movie that has 5.1 will win 7 automatically get it This is The only player that Plays SPDIF (Optical) The right way. But you have to Check the SPDIF in your Sound Manager and in the player (This is not for music)
Because Win 7 don`t do it Self when trying to play a Dolby Surround 5.1 DTS .....
This is the only way that I can get all my speakers to play if I am listening to music or watching a 2.1 stereo movie
All this is working on my Z-5450 speakers and SupremeFX II sound card but is will work with all. I be leave that buying a sound card is not going to fix this the right way.
Hope this helps you guys ....