Changing Latitude x300 Video Memory Size?

Ok, this might be a stupid question but is there any way to change the amount of shared memory the Latitude X300 uses ? It is currently set to 64mb, I have 640mb of ram in the system but 64mb vid ram is way over kill for what I want.. 8mb would suffice! I'd rather have more system ram available than useless video ram.

I have searched these forums, and all the manuals I can find and the only answer I can find is "over 128mb system ram will use up to 64mb vid ram" which suggests to me it can be changed, but I could be wrong.

Many thanks for any help..