Computer went from "standby" to "bye bye"

Hang 10,
you mention power pack, is this a laptop or a PC ?
Smell the power supply (if its a pc) does it smell cooked?
Open the side of the computer case up.. you see all the circular/prism shaped metalic things all over the motherboard.. do any of them look swollen?
are there any small green/red lights on the motherboard?
have you tried a different power cable (kettles usually have the same power cable) or even the monitor cable. make sure the cable is cactus.

also, there's usually a little black switch similar to a light switch on the powersupply. if you see this, flick it and try again.

short of that mate you could be in with a stuffed PSU or mobo!

I wound up buying a new power supply and it came attached to a new Lenovo desktop. I'm quite pleased at the moment. I've had old junk for so long, odds and sods of mix and match hand me downs and electronics snatched from dumpsters.

Anyway, thanks to all. I'm not naive about the Lenovo though. Lint in the form of an "Ask" toolbar has already managed to stick to it. I'm starting a new thread about it.