|Assuming you have the spdif cable connected correctly to the right places...|
(READ your manual for whatever the spdif headers are on)
You probably need to change the default sound output device to spdif from whatever it is set to now.
Control Panel - on the right of that screen have it display as Small Icons or Large icons, NOT Categories - click on the Sound icon - change the sound output device setting.
You may also need to un-mute the volume control for spdif there, and/ or increase it's volume from minimum.
"i tried to disable the onboard audio in my bios but that didn't work either."
You can disable the onboard sound in the bios if you want to, but you don't need to. (It has to be enabled if the spdif sound capability is built into the mboard, only.)
Win 95 and up supports you having more than one audio device connected to the system, but only one of them can be used in Windows at a time.
Whatever sound device you installed the drivers and associated software for last becomes the default sound device Windows uses, If you have the drivers and associated software for more than one sound device installed, you can change which sound device Windows uses for input or output in Control Panel - Sound. In the case of spdif sound, you probably have to change default settings, it's probably not made the default output device by default.
A HDMI connection on both ends has DVI video and a sound connection is available.
A DVI connection on both ends, or on one end, the other end HDMI, has no sound connection available.
A DVI port, or a HDMI to DVI adapter in a HDMI port, has no sound connection available.