First thing you should try is looking in the bottom right corner of the screen and open up the sound manager, take all the bars there all the way up, (Max Sound)
If you already did this, I'd recommend looking at Devices, in the control panel.
Look if you need to download/update any drivers for your sound. And look if the device is actually there, if it isn't there, either you sound port in your computer is messed up, or your sound system is messed up.
Hope this helpes, post here if you need more help