Ah I know this problem, and there is no single way to fix it because it depends on the hardware you have, including your case. For me, the grounding wire from the headphone jacks in the front of my case were also wired to the grounding wire from the front usb port, so doing anything on my computer (moving the mouse, playing games) would cause the noise of static synchronized with those events. My solution was to cut the connection between the usb and audio grounding wire. I also had the problem on an old P4 system, but it came through the integrated motherboard audio, so there was absolutely no way to fix that. If this is the case for you, then I suppose its possible that getting a non integrated sound card MIGHT solve the problem.
