If you are (1) planning on uninstalling and reinstalling NWN on the same machine, or (2) you have a new machine and want to move existing characters and games to the new machine, make backups of the following folders and files and copy them into the new installation:

FOLDERS (aka Directories):
dmvault
hak
localvault
modules
portraits
saves
scripttemplates
servervault

FILES:
nwn.ini
nwnplayer.ini

All are located under your main NeverwinterNights directory.