1stly it could be the source itself..
2ndly default settings could be wrong ( audio settings, choose 5 speakers)
3rdly onboard surround codecs, reinstall the sound drivers and chk.
I have a suggestion, silly but still works.
Use the kmp player, load ur video file.. in kmp codec for audio, choose ur speaker settings output to 5.1 channel.
in a 5.1 source, you will get d desired effect else go to point 2 and 3
but try the 2.1 source too... here if ur set on 5.1(via default sound settings and not speaker alone) and play 2.1, you should see some activity in surround cause ur set on 5.1. but then move the speaker setting back to 2.1 and leave default to 5.1, here you should hear sound missing....
I know i havent probably jotted d above well, but its 2 am mate and really bed time.... but d above is accurate and it works to chk sound
dude i just saw ur image
There is a setup that comes before the screen posted. is that rightly selected on 5.1???