never liked multimedia cards
u should have a mixer, so one thing u might do is to check if all the faders are up and unmuted.
u should also set your card to 5.1 mode instead of Stereo. It should be done somewhere in the driver's options.
Also, check Sound & Audio Devices in Control Panel, your settings may be different there. Pro cards usually restrict most of the access to control panel audio settings, so you rarely have problems like this.
