how to disable windows 7 shared memory

[Knight Of Shadows]

i noticed in windows 7 ultimate the system take around 1.7 gb of my memory and add it to the graphic card memory as shared memory

i know it's suppose to be a good thing but it's not . it's making 3D things become laggy

so i was wondering is there anyway to disable this in windows enviorment since i failed to located such option in bios

am new to windows 7

beside my memory are DDR2 and the graphic card is DDR3 so doubt they'll even work well together

i know when the memory is needed it will be used but i don't want it shared with graphic card memory !

any one can lend helping hand ?