Which operating system are you using? In Windows, the first thing I would check is to make sure the sound levels are not muted. (I've seen programs mute the entire system, not just that particular player)
You can try reinstalling the sound drivers. Go to HP support and enter your exact model number. http://welcome.hp.com/country/us/en/support_task.html
Do you have a headphone jack on the laptop? If so, try plugging a headphone in. Maybe the onboard speaker has failed.