The NavCoin data folder contains important files including the blockchain, the wallet.dat and the navcoin.conf. Messing with these files without knowing what you are doing can lead to the loss of coins so proceed with caution!
Make sure you have a back up your wallet before making changes to this directory. For information on backing up your wallet see this guide
The location of the data directory differs depending on your operating system. By default you can find it in the following locations:
C:\Users\YourUserName\Appdata\Roaming\Navcoin4
~/Library/Application Support/navcoin4/
~/.navcoin4/