Firstly Check and ensure that all the missing files are in the Pack you downloaded. Do a Search on your NWN directory.
If they are make sure those files are in the C:\Neverwinter Nights\NWN\Hak\ directory.
If they are not in the file you downloaded then grab the 1.52 hackpack as I know that has the required files in it.
I'm not sure if 2.0 still requires those files or if they have done something different.
EDIT CEP 1.52 can be downloaded
here
1.52 to 1.53 updater can be downloaded
here
If it asks to overwrite then don't but let it extract any missing files
Also make sure that there are files only in the HAK folder there should be no sub folders.