Did you connect the laptop to an external monitor to see if there would be any video signal going out from it? If not, try it and if it does go out, probably you will have to make an LCD inverter replacement. 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. In some cases, after much of a use and less cooling the GPU 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 have some 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.
Western Digital representative