|Have you, or is it possible someone else who had access to this computer...|
- dropped it, or dropped anything on it, or otherwise exposed it to a physical jolt ?
- spilled liquid on it, or sprayed it with liquid, or exposed it to liquid such as rain ?
Since the video last worked properly all the time, has there been a power failure event that happened while the AC adapter was plugged in ?
Those things are the most frequent reasons something inside the laptop has been damaged.
"half the laptop screen is dark"
There MAY be two backlights in your display assembly.
If the image on the screen is NOT sharply diivided, you probably have two backlights, one of which is not lighting up.
Your display assembly may have two backlights (CCFLs) behind the LC grid, one of them has burned out, or the wiring between the video adapter and the display assembly is damaged, or the display assembly has been damaged, or, a lot less likely, the voltage inverter than supplies high voltage to the backlights is not working properly. .
There's probably nothing wrong with the video adapter. If you connect an external monitor to your computer you will probably find there is no problem with the display on that.
Laptop no video (or video problems), and battery, AC adapter, power jack T shooting.
See response 1:
DO NOT plug in or unplug a monitor's video cable into / from a video port while the computer is running. Doing so can damage the monitor's circuits and/or the video adapter's circuits.
Some laptops will display on an external monitor without you having to do anything.
If you get no video on an external monitor, some laptops have a key combo that you must press to toggle the display to external video only / built in display video only / sometimes both - see the Owner's or User's manual for the model (e.g. press both Fn and Fx ; x is a number).