Easiest way is to pop the back off (remove the two screws on the bottom) peel the battery off and have a look at the printing on the NAND chip(s) - enter the string of characters into google to find out how big the part is. Remeber that 16Gigabits is only 2Gigabytes.
Then follow our glorious leaders thread on removing the hack if it is indeed a hacked player
How To: Removing Memory Hack