Picture/Game brightness

[peety]

hey guys, ive got a problem with my brightness/contrast. games and pictures show up very dark while everything else around it (start bar, text etc) show up nice and bright and clear. im running a crappy onboard SiS video card and a pritty old viewsonic monitor.. i cant change the video card as this isnt my computer.
anyone have any idea as to why something show up realy dark while other things dont? any help will be much appreciated.
Peety