ibm thinkpad R51e, graphic problem

i have this laptop, it has ati radeon xpress 200m chipset, and i have 512
MB of ram. i tought that i could change the size of ram used by my graphic
adapter by myself but now i'm stuck with 64 MB of ram used by graphis
adapter, and i can't change it... anyone has some ideas where to look? i
looked everywhere in bios but i simply can't find option for that. new
drivers maybe, flashing of bios? is it even possible to change amount of
ram used by graphic adapter?

tnx for any help...

Miro