pc switched off and won't go back on

Anyone got any ideas whats up My desktop switched itself off earlier and won't go back on. I have tried a few different cables just incase its that.

Its an HP Pavillion pc and it has a green light on the back panel which lights up when the pc is plugged in. This light comes on when I plug it in but when I press the button to power up the pc it goes off and the pc is completely dead.

maybe it is overheating so tripping out? this sometimes happen if peeps have had a PC for sometimes and let it get clogged up with fluff and dust but not cleaned it out?
smoking and dog hair adds to the problem as well.
try unplugging then taking side panel off and cleaning out any fluff or dust. be very careful when cleaning motherboard. only if you know what you are toucing, you can use cutton wool buds.
otherwise, go to Maplins or PC World and get a tin of compressed air and give everything a good spray around.

DONT hoover inside your PC, as the electro-magnetic static from a hoover can wipe your hard drive.

Thanks for replying I have done all that and its still completely dead

did you blast it with compressed air? including the fan an motor?

Yes everything is spotless inside. It usually gets cleaned out every month or so anyway with the compressed air because of all the dust and dog hairs.

Have you tried keeping the case open, when powering it up?
It could be over heating or the fan may be on its way out.
Other than that maybe its the power supply or motherboard.

Tried that too Marie

Was just going to say power supply or motherboard.
Think you're going to need someone to take a look at it.

Sounds like its the power supply if its not powering up at all, as if it was an over heating problem it would start up and when it got to hot then switch its self off.

i thought power supply as well.
but wouldnt that mean no green light?