I bought a Symphony Xplorer W70 Android 4 ICS. Its specification internal memory is 4GB=512MB, but now it shows 2GB. Why?
Manufacturers hide the user available memory.It's true that your phone has 4 GB internal memory but the apps,OS files needs space and hence you only have so less space.
Have a read at the below article so that you can make an informed decision next time you buy any electronic gadget -
8 Ways Hardware Manufacturers Are Deceiving You
well perhaps you installed applications so they took some space.
you can explore the space and see how space is used (big files...)