Improving my gfx performce [ bios ] need help



Ok I read on sites that if I have Bios Shadowing on it could lower my perfomance, I wanna know how to disable it. Someone told me to press Delete on start up but it wont work. Im using a Sony Vaio. my graphic card [geforce 4 ti4200] performance is really low and i think this might be the cause. Also how do I raise the voltage for my agp slot or something.