it could be that one of the sound objects is turned off? If you have the speaker icon by the clock right click and look at all the sections and see if one is muted. Or right click on the my computer icon - properties - hardware - device manager - sound devices and see if any of the options are disabled. Control panel - sounds then check all the options for any switched off or muted or with a low volume level. If all this fails then go to your sound system makers site and download the latest driver for it.