I have a Dell Inspiron N4030. It came with 2GB of RAM and is upgradeable up to 6GB. I brought a Transcend 4GB DDR3 RAM and installed it. I checked BIOS of my computer and it shows that total RAM installed is 6GB but when I check system properties it says 6GB RAM is installed but only 2.99 GB is usable. Why is that Happening? Is there anyway through which I can increase the usable RAM?

I use App2SD to move anything that will go to the sd card, freeing internal phone memory.