Windows 7 5.1 surround not working properly with external sound card

[spypsycho]

so, I have a 5.1 sound system, specifically the logitech X-540 and an external USB sound card that is supposed to allow me proper 5.1 surround. When I try the configuration on windows all speakers correspond when I click them and work just fine but when i play music or any sound, the sound only comes out of the Front right and left speakers unless I enable matrix mode which is not true surround though. any ideas on how to solve this???