Yes, I did check out the loading on the various calculators I found - in response to the suggestions - and there seems to be plenty of margin. More than the calculators suggest. Its 250W, and its only a main board, one hard drive and i3. No graphics card. The earlier psu that seems to have burned out was 300W.

I'm feeling doubtful that an inadequate psu can be the cause. Didn't note exactly what the restart message was. Something about going back to the last good configuration. No, I don't think there are two bios files installed. But there were a bunch of choices which I don't exactly remember.

What I did so far was to take the supply off the surge protected strip and connect it directly to the mains and everything is running fine now.

One thing that makes me suspect the psu is that the crash happened when watching youtube - which presumably is more processor intensive than just web or word processing.

Anyway, I ordered a new extension strip, this one brand named so maybe it will be better, and we will see.

I truly hate intermittent faults! Don't we all?

Al

On Tuesday 15 January 2013 08:01:00 Wayne Stallwood wrote:

As an educated guess I'd say either there has been a power spike/overload or PSU failure that puts it into protection mode or there is something going on with your mainboard.

When you say "The Gigabyte board asks me to pick the last good boot" what exactly is the message ? Is it falling back to a redundant BIOS image ?

Is the PSU adequately sized for the machine..I know we had this conversation late last year on the list. But specifically if you use a PSU calculator for your combination of hardware components does the current draw on the 12v rails come in at way under whatever it says for that rail on the PSU spec.

If you go by wattage alone you don't know if the distribution of capacity is sufficient across the rails for your hardware. You often can't for example draw the total rated capacity from one rail. Sometimes despite the overall rating appearing to be sufficient the 12V rail can be undersized, this is particularly true on PSU's designed for older hardware.