Computers are fickle objects. There are many pieces that come together to make a computer perform all of its operations properly. When the sound stops working on the computer, there are various factors that could be causing the problem, such as mechanical or software problems. Follow Windows guidelines to figure out the problem.
Check the sound card. Click the blue "Start" button. Click "Control Panel." Click "System and Security." Click "Device Manager." Double-click "Sound, video and game controllers." If your sound card is not listed here, install it using the sound card's installation disc. If there is a yellow question mark beside the sound card, right-click it and select "Properties." Click the "General" tab. Look at the device status box to see if there is a problem. If a problem exists, install the sound card again.
Inspect the speaker's cables. Make sure they are connected into the computer. The speakers will not work if any of the cables are not connected.
Turn the speaker's volume up. Click "Start." Click "Control Panel," then "Hardware and Sound." Click "Adjust system volume" under "Sound." Grab the slider with the cursor and move it upwards.