no it is impossible to change your graphics RAM on a laptop (unless you have an extremely expensive daughterboard gpu). You have 2GB hard, and the mobo steals 2GB from the system RAM (for windows desktop and cpu graphics chip)
hence it will read 4GB: 2 hard and 2 shared. but you only really have 2GB vram.
2GB is the maximum sharable memory allowed (stop thinking about increasing it with software/bios solutions - there isnt one).
- i will admit some gaming laptops do come with swappable vram slots, but its like finding a needle in a haystack cause sodimms dont perform as well as real vram chips (which is bad for games).