My housemate's desktop has a noisy power supply

[dieseljeep]

Originally Posted by user181

While grounding is certainly important, it will have no bearing on a noisy switched-mode power supply (SMPS).

There's been a trend for many years to provide an isolated ground for computers and similar equipment. It's not dependent on the raceway or the BX cable armor. It requires a separate ground conductor going back to the service panel ground bus. The bright orange receptacles you see in some locations are isolated ground receptacles.