When I switch it on, the screen comes on for about 5 seconds then goes off again. The whole thing goes off, not just the screen.
It does the same with or without the battery connected to the mains, or just with the battery, so not a battery problem.
The hard drive is OK. I've taken it out and can read all the data on it (by connecting it to another computer, not using a magnifying glass ).
I've taken the whole thing apart but can't see anything broken that looks obvious. I powered it up with the screen off, the DVD drive out and just the board and processor getting power. The fans spin up for the 5 seconds then it dies.
Motherboard or processor problem?