Have you tried checking the speakers to make sure they are working? Here is my sound testing process.
- Get an MP3 player and some headphones.
- Plug the headphones into the MP3 player and make sure it plays music.
- Plug the speakers into the MP3 player and listen for sound.
- Plug the headphones into the computer and listen for sound.
Step 3 makes sure the speakers work, step 4 tests the output device.
Once you check that, you need to make sure the sound isn't going to a different device. If you have multiple playback devices, disable them. Make sure that the default device is set to the correct device. Restart your computer and try again.
If it is still busted, open a few programs that play music. Start a song and take a look at the sound mixer. You should have an column for each program. If you don't, something is wrong with the device/driver.
At this point, you will need to make sure that you computer is capable of playing sound. This means you will need to install a new USB sound device. Generally, you will have to buy a USB headset to test this.
If you can't get sound on a USB device, then we'll need a lot more details and maybe some screenshots to help you more.
Hope this helps