I have an HP G71-329wm computer, and want to upgrade video card, is this possible?

The current video card is Mobile Intel 4 Series and I need to upgrade to 256 Nvidia7900 or ATIx 1900 video card to play games. Im not sure if I have an open slot to do this? Anybody know if this is at all possible? or a good idea or not?|||You cannot upgrade videocard for laptops.