|See the User's or Owner's manual .|
Some laptops have a key combo for adjusting the brightness of the built in display , or two of them - one for increasing brightness, the other for decreasing the brightness, and another key combo that toggles the display - built in on / external on / sometimes both.
When do you get a black screen ?
All the time, or you get video while booting every time but not after Windows is supposed to load?
The latter is caused by a different problem.
The former can have several causes, including
- the main battery doesn't have enough "poop" when the AC adapter is not plugged in, usually because it doesn't have enough capacity left because it needs to be charged. Plug in the AC adapter. If you still get no video, hold the power button until the computer shuts off, let the battery charge for awhile, then try booting the computer.
- you reloaded Windows from a regular CD or DVD, but you didn't load the mboard's main chipset drivers, the computer went into Standby or Hibernate mode, the screen went black, it won't come out of that mode - hold the power button until the computer shuts off, press it briefly to boot normally - you will have video. Load the main chipset drivers.