Ok if im getting what your saying
the port of the computer for line in is not recognizing the sound of your sterio
ok there should be extra jack on speaker wire that should goto line in on computer
computers dont find these jacks cause there already predetermind when the cards drivers was installed
hook the jack to line out speaker out port if the speakers are powered find the power on them turn up
then goto your sound setup get to your volume controls and find the volume controls that are muted and or turned down even in advanced settings
if you recently changed your sound card you also want to be in the sounds setup and make sure that the propper software driver is connected and not the old one still in its place sometimes new drivers dont set the old drivers aside but it adds to the sound setup list
you will find the sound setup in control panel
also there is that slight chance you will have to reinstall software again
hope this has some help for you seeing i have no way of actually seeing the speakers in person and how they work