My computer screen is very dark but I can get to see the data. Cause: The inverter or inverter.
If your laptop screen is very dark but when you connect an external monitor to your laptop to the VGA port perfectly see the beginning of your operating system probably do not have to change the display but a piece called inverter or inverter.
If we see the data on our screen is due to a light bulb gives located on the rear LCD screen, and the part that supplies power to the bulb is the investor, which is normally located at the rear where is the screen.
Whenever we come across a dark screen, in most cases is because the inverter is broken. On occasion we have found that failed the screen giving the same symptoms when the inverter fails.
To know what is the investor who is damaged try changing the screen as you or other simple, try to connect as stated above, an external display VGA port of the laptop, if you see data that you already know that change the inverter.
More advanced users can also test the inverter connecting the lamp that gives light to the screen, if the lamp does not light the bug is in the inverter, if the lamp is lit, the fault is on the screen.