In all honesty I wouldn't expect a power supply to fry the computer due to AC power variations. The low voltage section is for all practical purposes insulated from the high voltage part. A PSU would have to be really crappy designed to fry the board. I'm not saying it cannot happen (it can and I've seen it), but it's an extremely rare occurrence if the PSU isn't the kind that is pre-installed on a $25 computer case.
Now the high voltage part is indeed subject to failure and transient conditions can cause the magic smoke to escape - but again it shouldn't cause an overvoltage condition in the low voltage section.