First, you are running vista home premium.
home premium does require a huge chunk of your graphics
memory.
secondly, you are using integrated graphics, thus, it is also
called shared graphics. this causes your vista and wow to, in
layman terms, compete with each other for the graphic memory.
One way to do it is to turn off all the fancy vista graphics
intense things - like flip 3D, aero interface.
alternatively, you can turn your computer to windows theme to
windows vista basic or windows classic. (classic reccommended)