Is it plugged in? take the side off your pc and make sure there is a cable running from the front port, to the motherboard.
Might be listed as AC97 or HD Audio on the motherboard.
Do this. And also check that no audio outputs are disabled within Playback Devices. Leaving music playing, and checking Playback devices will show which speaker is trying to play audio, even if sound cannot be heard. You should see a green bar at the side bouncing up and down like an equalizer does. Make sure this output is set as the default audio device. Close whatever application was playing audio, re-open it, and it should work providing no hardware is damaged.