BANG!
This evening I was passing the study on my way to a nice, hot steaming bath when I heard a BANG. I wandered in, to a smell of burning, the lights on the desktop computer "off", and the monitor showing "No signal". A gentle wisp of smoke was curling up from behind the desk.
I promised myself it was the power supply, and fished out the spare from the cupboard. Amazingly, it WAS the power supply (I suspect the fan packed up due years of dust). All is back together and working, and I've been to Ebay to order another spare.
That's the fifth power supply I've changed in the past six months - most of them in other folks' computers. I didn't bother to check this time, but the others were "fan seized up".
Do folks reckon hoovering out the case every six months or so would help?