After I power it it, the harddisk only blinks once (almost invisible), and then the fan is making noise while there is nothing on the screen.
I went to a diagnosis shop and they tested memory, and battery and reported no problem. When they removed the harddisk and then rebooted, I can see there is a line on the screen "PCI express failure", etc.
They said that they were able to see the content of the harddisk by plugging it to another computer.
So what's the problem? Thanks!