First of all, try different sound devices. You can borrow a set of speakers from your friend to see if there is something wrong with your device. If no device is working properly, you need to take this matter a bit seriously.
Click on the ‘Start’ menu, and enter the "Help and Support". Click the "Games, Sound and Video Problems."
You will find an option that says "Sound Troubleshooter." As you click on it, the sound repair wizard will launch. You will have to go through a series of steps here. Keep clicking ‘Next’ until the process is completed.
If you are still facing the same problem, you must re-install or update the player you are using to play the audio files. Sometimes, the media player doesn't work properly and as a result, the user receives no sound.
If you are facing the issue even after installing the media player, there is certainly something wrong with your sound driver. To update the driver, go to the ‘Start’ menu, and run "dxdiag" (without quotes).
A window will appear. Click the ‘Sound’ tab on it, and locate ‘Device’ section. Here you will see the complete details of your audio hardware. After writing down your audio driver's name and provider, click ‘Exit’.
You may have a CD of drivers. But if it is not available, you can update the driver online. By using the information that you wrote down, get the latest update from the ‘Downloads Section’ of the driver manufacturer’s website. Once the update is done, your audio device will start communicating with the computer.