Maybe you have accidentally told the laptop it needs an external monitor. Hold the Fn key down and locate the function button which switches between laptop screen, external monitor or both.
Press it once while holding the Fn button down - anything? try again, try again coz there are 3 modes.
Failing that - start up windows in safe mode - power on while clicking the F8 button - a menu should pop up and select safe mode - then andjust screen resolution to a lesser size - try 600x800 first - reboot.
JonnyHog
November 2010