I am harpreet shergill i want to ask from you that when i turned on my laptop the screen is fully blank and in key board lights are on and fan is running .
so please tell me that what i have to do.
The problem you have could be due to the problem with the video chip. Sometimes, after much of a use and less cooling the North Bridge - which is responsible for the video signal gets desoldered and its thermic "paste" goes away therefore the screen doesn't show anything but the fans are still running. If you understand notebooks hardware you can do it yourself, opening the laptop and see the chipset that is next to the processor if has been unsoldered or bring it to a technician to get it soldered again.