Its a fairly old VAIO PCG FX500. It was turning off after a few mins so I figured it was overheating. Opened it up and hoovered the fan, and the vents, (careful not to touch anything)

Now it turns on for 1 second then goes off. No bleeps to suggest motherboard or processor.

I have got it open and when it switches on the fan spins and cd drive clicks once then straight off.

Any ideas.

Now working, I think it just took a while to cool down to the point it was happy to switch back on again.

Often when they are open they won't turn on, I have found this strange thing with some laptops I have repaired, I have diagnosed the fault, gone in to fix it, tested it outside the case, it's not work, I have given up, re-assembled it again, and tried it 'just incase' and they usually work at that point..

Strange I know, but hey... it happens :)