Just color it with a permanent black magic marker.... Just kidding. It depends on your laptop since each model is somewhat unique. If yours doesn't have any knobs or buttons then it is software based and you will need to find the program to do it. My E-book has an icon in the lower right as my task-bar for windows vista is on the bottom. The icon looks a bit like the plug to a power cord on top of a battery. This is where I can access settings involving how much power my laptop uses, including how bright or dark my screen should be. I hope this helps you.
Its very easy yaar .... You just keep holding function key and press the many time down arrow key to make the screen darker. If you want to increase the brightness then again you press holding to function key and press the up arrow key many time's, not only every ones screen will become brighter. More information contact