Speakers plugged in? Try plugging in another pair. Or, reinstalling your sound drivers.
How
Insert speaker plug into speaker socket.Get other speakers and plug speaker plug into speaker socket.Go to 'Device Manager' through My Computer and find your sound drivers. Click Troubleshoot.
Click on your primary sound controller, for my speakers it's RealTek HD Audio, for my headset it's ATi HD Audio.Click 'Update Driver'.