|The internal backlight of the laptop has failed. Meaning that the monitor is not bright enough for you to see. you can do one of two things|
1. use an external monitor cable to connect to a second monitor
2. open the case and replace the backlight/check wires.
I had the same problem with my first laptop. The backlight died and I was unable to use it. I baught a cable and connected it to my TV it worked fine.