How can we fix black screen of Lenovo Dolby G-40?

I had the same issue with my lenovo a few weeks ago! Does the power light come on? If no lights come on when you push the on button and plug it in (which is what happened with mine) it could be one of several things: the power button could be broken, there could be something wrong with the adapter and the battery is run out (try using a different charger) or it could be the motherboard (in my case). If it's the motherboard there's nothing you can do, but explore the other options first. If no lights are turning on at all thats not a good sign, you may need to get a new laptop.

Do NOT mess with it, you may cause the system to crash. W8.1 has downloaded and is now configuring updates. Look at your HDD light, it is likely blinking, meaning the OS is functioning. W8 & 8.1 are notorious for periods of "black screen" during this process. Once the OS has finished the login screen will display.

We've tried reformatting it. We've inserted a windows 8.1 cd to install the OS but the laptop has still no response. Last night, we've tried holding f12 and the power button but is beeps. Then, i turned it off. Then i tried it again. Then the boot menu manager appeared. But now, it is not working.