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.