bibhash , you will need to format your player as 4GB nano-clones do not exists physically yet.
However, rather than using Windows to format as amnman had suggested, as usually Windows will still read and format it as 4GB. The idea of the memory hack is to trick the Windows operating system into thinking it is 4GB, so formatting using Windows will still not remove the hack.
Use the MP3 Utilities Disk Tool that either came on the cd with your player, or download from the forum.
The guide to performing the format is
Here.
To further verify your player's memory, you can open up the player and check the memory chip's serial number against the manufacturer.