How to modify the assigned VGA memory in Inspiron 1300?

Hi, everyone.

I have an Inspiron 1300, originally shipped with 512mb (256+256) of DDR2 RAM modules. It showed in "dxdiag" 128mb shared memory for the Intel 915GM/GMS.

But now, I've changed (twice) those modules with others to upgrade my laptop to obtain 2gb of DDR2 RAM.

Firstly, I used one 2gb Kingston DDR2 module, but I observed in dxdiag that there were just 96mb for shared memory... strange.

After that, I tried with two Samsung DDR2 modules of 1gb, the same brand as the originals, but the amount of shared memory stays the same: 96mb.

How can I change that amount to increase it??

Thanks for the responses.

P.D.: The BIOS can't arrange the shared memory, it's a fixed value.