Hi there, it's me again with more trouble

I've been trying to configure an old 5.1 ANALOG system [no hdmi or other digital sound plugs] but for some reason, the media players [Media player Classic from k-lite codec pack, and windows media player] just don't give a surround output, only stereo.

I've tried to modify the ffdshow audio decoder option to config it to 5.1, without luck. All I could find around the internet is also about digital surround systems only. So, any help? I'm sure I have to config it manually at this point, just dunno how.