Open you computer, in the HD there should be a black or white rectangle where a bunch of pins are located, remove that pin and try again, that tells the computer that the HD is no longer a master but a slave.
DISCONNECT UR SCREEN. Turn it on, if u see the screen light up (backlight), monitor works... well at least back light. Reconnect it back to ur comp. Turn it on, turn on pc. Probably got ur cable disconnected.