its taken by the onboard vga graphics card.
it can vary from anywhere between disabled, 512 kb, 1 mb and 8mb
so do one thing boot into ur bios.pressing del key
and change this property to 512kb
i am not sure of disabling though as i myself had done once and nothing was displayed on the screen.i had to guess which key i had to press remembering the last time i was there. it was tuff....real tuff to remember and press exactly the key needed.
but since u have a graphics card, so i dont knw whether u will face the same problem.
but i advice u too keep just 512kb.