whining psu noise

Hi guys, I just completed a first build. All went well with the exception of one thing. Once windows has loaded, a electronic buzz emits from, I believe, the Enermax 350W power supply. It is definately not fan noise. The whining starts when I use the mouse or keyboard to scroll through the Windows' start menus, and stops as soon as I finish. Sometimes the noise just stays on until I tap the mouse or keyboard.

I swapped the psu to an older computer...no buzz. I unplugged my speakers and swapped the mouse and keyboard...buzz continues. I have an older, cheaper psu that I did not want to use on new computer out of risk of damaging it.

I understand that some psu normally make a whining noise. However I'm finding this noise to be annoyingly loud. Is this grounds to replace my Enermax psu?

Any help on this matter would be greatly appreciated. Thanks.

AMD2000+, Volcano9+, Asus A7N8X-DX
512MB Samsung (1 stick)
ATI Radeon 9500 pro
LG cdrw 48x24x46, Liteon DVD 16x
WD 40GB
Enermax 350W
Lian Li p65u
Windows XP pro

By carefully listening to various parts of the computer, it seems like the noise is coming from the psu. However, I'm confused as to why the noise went away when I installed the psu into my older computer. Could it be that some of my components are incompatible? Or, is it at all possible the processor could emit non-fan noises?

Also I should clarify, the mouse movement itself does not start the noise. It's when I use the mouse or the keyboard to scroll through the start menu items and programs that the noise occurs.

The noise isn't excessively loud. It's just becoming quite annoying.

LHGPooBaa, thanks for your input.

I ran the computer on a heavy load (Prime95, a South Park episode on DivX, Asus Probe and an mp3), and noise becomes constant. When I shut down the programs, the noise ends.

I'll try exchanging the psu tomorrow. Thanks again.