Is there an audio interface in the equation?
Sounds like ground loop problem with interface connected to pc I've had before.
* Back of profiler, there are series of red buttons which are ground lifts- if you haven't already- try pushing those, see if anything changes.
* if you have more than one device connected to your audio interface (inputs and outputs - anywhere), disconnect them until noise stops. Troubleshoot from there.
*You could always test your house wiring, but pretty unlikely that's the cause. You can get a tester at a hardware store for cheap. Really doubt that's your problem, though.