Some motherboards can support uneven amounts of memory in Dual channel, so the only way to tell is by knowing your motherboard model number.
So post the model of your motherboard for further help.
Deli, you are still talking about preloading TWO items? Preloading TEXTURES and preloading SKINS right?
Hajo, when you press CONTROL + I, what does AH report for USED SYSTEM MEMORY?