We have a PC that's a component of a much bigger system. The system
uses European-style power (it was made in France), so the computer's
power supply must be set to 230 volts. After some recent maintenance,
someone forgot to set the PC back to 230 when putting it back into the
system. The user turned it on, heard some loud pops, and unplugged it.
I was called in to help from there.

The power supply smelled like smoke, so I replaced it. When plugged
in, the power supply makes a very high-pitched noise and the computer
won't turn on at all. I tried replacing the processor, memory, video
card and unplugging everything else, but this did not fix the problem.
I replaced the motherboard, no dice. I have tried two other power
supplies, another processor, different memory, etc. Basically,
everything that's hooked up in the system is new, but the power supply
still whines and the system won't boot. The power supply only makes
the noise when the main power connector to the system board is
attached.

The system is a Dell XPS R450 with an Intel P2 processor (yes, it's
rather old). Some documentation: http://support.dell.com/support/edocs/systems/dkhan/

I'd really appreciate any suggestions anyone might have.

Thank you,

Ben