ur ryt heshi32.
wenasak atha.
If u r using 2 2GB RAMs in dual channel mode it will give better performance than 1 4GB RAM. However for this you need a motherboard supporting Dual channel mode (almost all motherboards nowadays do have it though) & 2 memory sticks of same capacity, same speed and same make i believe. (eg:-2 x 2GB Kingston DDR2 800 sticks)