Has anything happened to the laptop prior to getting this error? Are you able to hear the fan and/or the hard drive spinning or everything remains calm? My advice to you would be to connect the laptop to an external monitor to see will there be any video signal going out from the laptop. If it does, then you need to replace the LCD inverter. It may be the cable or the tube. If there's nothing showing either on external monitor nor display, but the fans are still working, the problem that you have may be due to the failure of the video chip. Sometimes, after much of a use and less cooling the graphics processor which is responsible for video signal transmission get unsolders, the thermic paste goes away and it gets unsoldered, therefore the screen doesn't show anything. If you possess knowledge of notebooks' hardware you can change the paste yourself by opening the laptop and check if the chipset that is next to the processor has got unsoldered or you can bring your laptop to a technician to get it soldered again.