Whatever kind of laptop you have (DELL, HP, ect.) go to there web site and look for support / downloads / drivers. might not be in that order but you get my drift,
Here is Dell's support site for laptops http://support.dell.com/support/index.aspx?c=us&cs=19&l=en&s=dhs&~ck=mn
Your looking for your sound driver. Download the driver to your desktop or somewhere that you will know where it is, run the program and all should be well.
One other thing you might want to try, plug in some exterior speakers and see if that works. I'm asking this because I don't know what you've tried.
If I knew what brand of computer I can give you the site you can go to, and also If I knew the model number I can give you the exact page to download it from.