Dual moniter Video card on/off toggle

Hello,

im running dual moniters using an onboard video card (NVIDIA GeForce 6150SE nForce 430) as well as an offboard video card(NVIDEA GeForce 8600 GT 1gig)

the set up has been wonderful except when i run a few of my normal high end resorce hog programs... running the onboard video card boggs down my system, i was wondering if there was a way to toggle the onboard video card on and off with a hot key or something so that i can continue running my programs without theresorces being hogged up

thank you