The .nss files are the Nwn Source Scripts that are in plain text and use the nwscript language. They contain the instructions that tell the game what to do, works more or less like a recipe (ex. make the pc walk from point A to point B, add a npc to your party, spell effects, spawn Mr. X when the pc has done something, etc). You can open them with notepad but I doubt you will find them useful unless you want to make mods. However, .nss files do not have any effect on the game unless they are compiled. When you compile them, you get a .ncs file which is what the game uses (more or less like the cake you get after following a recipe :p).
If you want the dialogues, what you need is the .dlg files. Here a short tutorial I<ve put together for you:
1. Extracting files with findrefs:
Let's say you want all the *.dlg files that mention Coruscant. In order to search them with findrefs, you have to check the "Include TLK file references", select your game and search only .dlg file (you can search all the files but it will be useless if all you want is to access the ingame dialogue.
If you look at the screenie below, the .dlg files are listed in the middle column. The left column indicates the module (ingame location) where they are to be found and the right column indicates the Entries (what npc say) and Replies (what the pc says) lines numbers where the word Coruscant is mentioned. As you can see there are about 20 results but only 11 different .dlg files (003atton.dlg, bardroid.dlg, etc).
Screenshot (
http://img.photobucket.com/albums/v144/Darth333/dlg1.jpg)
BTW, the name of the .dlg file with the council scene is holorec.dlg. Just type holorec (don't put the extension) in the findrefs searchbox, select "search filenames only" and select .dlg as "file types to search".
2. In order to extract a .dlg file, simply click on it to select it (you can use shift click to select more than one file) and hit the "Extract Selected files" button and finally select the folder to which you want to extract the file:
Screenshot (
http://img.photobucket.com/albums/v144/Darth333/dlg2.jpg)
3. Fire up DLGeditor by double clicking its icon and open the .dlg file you just extracted (File menu->Open) and you should see something like this:
If you mouse over the line where I added a green circle and an x on my screenshot, you can expand the treeview (left click). If you go to the View menu, and select "show Indices in Tree" you will see the Entries and Replies numbers. The numbers in the right column when you search with Findrefs, correspond to those same numbers.
Screenshot (
http://img.photobucket.com/albums/v144/Darth333/dlg3.jpg)
For movies, you need Bink from that page:
http://www.radgametools.com/). Movies are installed by default in your C:\Program Files\LucasArts\SWKotOR2\Movies folder. If you have the RAD video tools installed, just select a movie in your folder and open it with the Rad Video tools.
Option b : Extracting .dlg files with Kotor tool instead of findrefs:
General banter:
select your game and go to BIFs->dialogs.bif, select your file and hit "Extract file"
Screenshot (
http://img.photobucket.com/albums/v144/Darth333/kt1.jpg)
Module specific dialogue:
Go to Kotor 2->ERFs->Modules, select the module (game location) where your .dlg file is and click on Extract file.
Screenshot (
http://img.photobucket.com/albums/v144/Darth333/kt2.jpg)
And then, follow step 3 above :)
Hope this helps!