Problem with Screen Brightness?? Dim in Battery Power? Go to BIOS

How To Adjust Laptop's Brightness, When It is Not Responding.
I had recently faced a problem in my Laptop's Brightness. My Laptop setting by default is, that in Battery Power, the Brightness is automatically reduced or dimmed, to save battery power. If I had to increase the brightness ( both on Battery or A/c Power mode), the simplest way was ,keep pressing Fn (Function) & with another finger Up button till my desired Screen Brightness. The same thing I do to dim or reduce the Brightness of my Laptop, to save energy or increase the working time of my Laptop. Recently I faced a problem that the Screen Brightness of my Laptop was not responding to Fn + Up or Fn + Down arrow button. So what was happening was quite irritating. Whenever the power comes , the panel brightness become full, that is brightest & whenever the Laptop runs on Battery, the Laptop's Screen Brightness become very dim that is to lowest. I was not able to see properly to my laptops desktop in daylight.
All these happened due to worm infection to my Laptop, that reduced the brightness to lowest level. Adjusting the screen brightness, by control panel did not work at all.
If you are facing the problem of this kind or even not facing, you can adjust your Screen Brightness by modifying BIOS Setup. BIOS is Basic Input Output System. It contains all the information about your system & the setings, that is adjusted through Factory or Inbuilt settings.
HOW TO OPEN BIOS SETUP or SETUP:
Restart your Computer--> keep pressing F12 ( or see for which F button is for BIOS/Setup)--> BIOS SETUP will open.

How to Adjust Brightness:
Go to Video option in BIOS by pressing DOWN arrow button on the right side of your keyboard--> Brightness option will drop down, click it--> Brightness Adjustment will be seen on right side--> Adjust it as you desire--> save it & exit setup--> DONE.

See in above picture( not the actual screen shot, I made it in Paint :-), but the actual screen looks almost same) , the factory default setting of my Laptop Screen Brightness is 3. You can adjust it to your desired level, to Full, to enjoy the full Brightness, even in Battery Power.
If you miscued or missed the Video button in BIOS SETUP, you can always go back by pressing ESC button.
** Imp: For going to BIOS you have to quicly press F12, as it is shown for a millisecond, or else you have to again restart your Laptop. The best way is keep pressing F12 as soon as it restarts.
ENJOY & keep reading.