Computer sound wont work but everything shows its working

Are all your plugs in correctly(USB plugs on motherboard and your audio or HD audio cable)how about your front panel connectors.Go to your control panel and click on Hardware and sound.Click on "sound" and then "manage Audio Devices">>>From there it gives you all the items you can enable or disable. Enable the sound to the device you want to work.If it is on board,then it will have the name of the on board chip.Or in your case you have a Realtek card.I had an issue like this and I just tinkered around a bit and wa la -- the sound was working. Also make sure your card is seated correctly in the motherboard,and power is connected.

If you are on vista, or XP, it might work on Win7 also, i'm not sure, click on the start button in the bottom left of your desktop. Go to control panel, navigate to hardware and sound, click on it then navigate to sound, click on it, a window should pop up that has 3 tabs at the top, maybe more or less, in the playback tab, make sure speakers are enabled, then go to the recording tab and make sure stereo mix is enabled. If that doesn't fix it your sound card is probably fried. Or maybe someone else has a solution that does work.