If your display stays dark, it may also be some short-circuit. (However, harddisk is more likely) My son caused short-circuit to my Samsung NB28 by connecting phone charger to laptop LAN-port. After that my computer just clicked and lights went on and off after starting. Taking battery out, didn't help either. I opened the laptop and connected the two tin-spots on circuit board, which had small text RST (means reset). After that my laptop started to boot again without clicking sound.

Instruction was working well. I had problem with only one button on the side of the display. I cleaned the contact surface of the button with the isopropyl alcohol. It had some small dust. Now the button is working much better, but it is still not perfect.

I think that the problem is with the black metal (magnet?) which has wear. Thanks for helping ! Great forum/guide.