Why is my internal storage of 8gb not showing when samsung SM-G7102 is connected to a computer?

[AC Question]

Hi forum,
I have just purchased a Samsung Galaxy Grand 2 Duos. When connected to the computer it shows only an internal storage of 2gb and my external SD card of 8gb but the remaining 5gb doesn't show. I am using a computer running Windows 7 Enterprise 32-bit with 2gb of RAM installed. Please help.
Daniel