there are four possibilities:
1) a sound cable/wire in your laptop has been broken and needs to be re-soldered (4 can be done at any computer store or maybe a music store like guitar center)
2) the speakers could be blown up. in that case, you would need to get new speakers installed into your laptop. to test for this, try plugging headphones into your computer and see if that works
3) there is something wrong with your sound card. bring it in to a computer store and have them look at it
4) your sound card needs an updated driver (best case, requires internet). to check for this
a) press the start button near the bottom of the screen
b) click the control panel button
c) double click on the system button (it has a computer with a check mark on the screen as its picture)
d) click on the tab that says hardware
e) click on the button that says device manager
f) click on the tab that says sound, video and game controllers
g) figure out witch one of the devices that it shows is your sound card
h) go to the website of the manufacturer
i) download the driver
j) install the driver