[NA Blur]

A few things to try:
Once you get music playing on the PC try removing each USB device and see if the noise goes away. It can be a bad mouse, keyboard, or other USB peripheral.

 

[rishan]

Thanks for the help guys, unfortunately, the cord from the ground to the box didn't work. I also tried removing every device including the HDMI and displayport outputs. I've ordered an iDefender 3.0 which should basically allow me to covert a USB out port on my computer to data only, then feed the defender with clean power from a separate source. Will report back on if this works!

 

[NA Blur]

Yeah PC listening can be hassle in the USB domain. I stay optical myself.

 

[bluecar]

Your PC is the problem. PC's are assembled using a mix of parts from different manufacturers, conforming to a series of standards for peripherals. The internal space and layout is dictated by the components, and as a result shielding and power routing suffer. Apple, on the other hand, control every aspect of the internal design, including the physical layout, and they optimise for heat management, RF shielding and EMF protection. They also tend to choose decent interface designs, to support their (substantial) creative base, who make heavy use of USB for video and Audio applications. Unless you can hand-build your own PC (perfectly good option), Mac offers a better out-of-the box solution for USB audio.