i have a ULTRA 550W Modular PSU. it makes a rather quiet but really annoying high pitched whiny squeaky sound. when my system is under high load it does it slightly louder. why does it do this and is it bad?
thanks in advance!
It's from one of the transformers or coils in the PSU. One or more of the coil windings is a little loose and the changing current through it causes it to vibrate imperceptively.

It's a sign of poor quality control more than anything else and it's more annoying than a critical problem.