Brightness in games >>>>>> go down

[novalogic88]

whenever i play a game such as counter strike, sirious sam or fall out:tactics, my screen brightness will go down as soon as i get into a game, i have to manually adjust it through the OSD (on screen display), its not a big problem but its just really annoying, does anyone know how to fix it, i had it on my old geforce2 mx as well as my new hercules 4000XT kyro 1 card, PS: i reinstalled my computer after i bought the new card.