what becky said probably depends on the graphics card in the machine and the software you have installed for it, i don't think that is a standard windows feature, it gets "injected" by the video card software. if you don't see these controls, figure out what's in your laptop and get the software/drivers from their website (ati or nvidia)
I got a Dell inspiron 1200 and I can't figure out how to change the contrast.
Called tech. supp. a few times, once they said you can't, another time they said to press the FN key and the left and right arrows, but that didn't work.