Mysteries of the Soundcard

There were different players installed for playing soundfiles.
But for some reason, the soundcard will not work.
The only sound is comming out from the left front side speaker.
Except playing a (video)-file from Youtube. Suddenly surround is working.
Absolutly confused.
Using Win8.
With XPSP3 surround is working like it has to do.
But for some reason, the soundcard will not work.
The only sound is comming out from the left front side speaker.
Except playing a (video)-file from Youtube. Suddenly surround is working.
Absolutly confused.

With XPSP3 surround is working like it has to do.