I an trying to install PRC. The PRC spells works on nwn, but i can't use the character creator. When i click to create a character, an exception happens.

You should really ask on the forum related to the particular mod.
Two things that you should be doing anyways regardless of which game or modding is:
Install things out side windows folders, never under any circumstances install things to program files as this causes unrold problems. Create a folder like c:/mygames and install there.
Next, do not use galaxy. Download the installer files from the web site and install it from them without and galaxy part. Who knows what galaxy files are additional or interfering.