If you think your computer speakers are malfunctioning, try the following:
1.) Ensure the speakers are in fact the problem by testing them on another computer, or test your computer with another pair of speakers.
2.) Move your speakers as far away from your computer's electrically noisy power supply as is possible.
3.) Buy another pair of speakers; they're inexpensive.
you should test the computer with known working speakers. if they work, then the bad speakers need to be replaced. if not then the audio card needs to be replaced.
If the problem is that theres lot of noise and disturbance in the audio, then the problem could be rectified by re-soldering the wires inside the main speaker box.