Inspiron 1545 integrated graphics

Hi,

My laptop's total graphics memory is 781MB. I got this information from the Intel graphics properties menu. Also by running dxdiag.

But in the BIOS the graphics memory is set as 32MB which i feel is far very very less.

I want to increase this graphics memory in the BIOS but it doesn't allow me.

Why is it so? 

I have done the same setting for my desktop but why is it not allowing me to do in Inspiron 1545. 

How do i change the BIOS settings?

Dinesh.S