Volume issues

so i have an ht omega striker sound card which takes any sound and encodes it digitally into whatever signature. i have the logitech z5500 5.1 system connected to it via coaxial. everything works fine except the volume for the front left and front right speakers cant be controlled by the main volume for windows. however in the volume mixer i can adjust all the speakers by changing the sound volume under the application volume controls. i imagine that this is a quick fix. any ideas?