It sounds like the cable or plug coming from the computer to the speakers. Try connecting the speakers to an MP3 player or something with the same audio output jack. If you have the same problem, it's going to be the speakers.
Just as common as wear and tear in the cable and plug is the wear and tear of the volume switch. It might just be time to get new speakers.
Most computers will delay when playing music at the same time as running some applications. If your computer is taking a hell of a time, try a spyware scan with Adaware and Spybot Search and Destroy (found free with a google search).
Good luck.
David
February 2007