Hum's not software (almost never is),... what you are likely getting is the kind of ground loop effect that they were describing, but perhaps due to the way the manufacturer of your PC configured the sound system,... So very possibly, it's internal to your PC,... But process of elimination, try changing what power source (what outlet/breaker the machine is on versus to speakers/AMP/TV) the things are pulling from,... ya know,... moving them all to the same, or making them all different, etc.