Open your nwn folder. Find the following exe files and change them to run as xp compatible ( right click on file, select properties, click compatability tab and check 'run as xp compatible) if you own Vista...get used to this

nwn.exe
nwmain.exe
nwloader.exe
Vista also seems to hate EAX sound, so make sure EAX is turned off under sound options.
Also, if you have dual core processors, you can force nwn to run on a single processor. Seems to make it run smoother.
Open nwn folder, open nwnplayer.ini file.
change Client CPU Affinity from -1 to 1. the -1 sets it to run off all processors. Changing it to a positive number sets the number of processors to use.