i had the same problem a few months back with my dell comp
ok well what you do is go 2 your computer companys website eg dell
- then go to your style of comp eg if its a home or office comp
- then go 2 support
- then go to drivers and downloads
- then choose the model of your laptop
- then go to audio which is a catergory under the pic of your laptop
- then download anything that has sound in the title, they can also be found in the application catergory

i personally had to download soundmax and that fixed it right up
sorry about it being all about dell, it should be similar steps for other companys if your with someone else
good luck!