unpack the ini?....phewy....lol...ok...I'll talk you through what I do with my inis and hopefully you'll get the idea -
1) create a new folder (preferably on another hard drive to your game....but if not, make sure it's no where near your game folders). Call this folder MyMods.
2)create a folder in MyMods called orginal ini (this is where you copy your original unmodded ini.big file).
3)create another new folder in MyMods called My Moded Ini Uncompressed (this is where you'll unpack your unmodded ini to).
4)create yet another folder in MyMods called My Moded Ini (this is where you'll put your moded ini.big saved from FinalBig).
6)copy your original ini.big to MyMods>Original Ini
7)Open FinalBig and select File>Open and navigate to MyMods>Original Ini and open your ini.big that you find in there.
8)in FinalBig select Edit>Extract All (you'll get a message come up about extracting the files and that any files will be overwritten....just click yes). Then navigate to MyMods>My Moded Ini Uncompressed (you just highlight the folder in the tree view) and click ok....it will then extract the files to that folder.
You can then copy the extracted files from the location if you wish, or leave them there.
Usually I create a new ini.big to over-write the one in the game directory (I have backups of the originals).
To do this there are some extra steps once you've moded your ini files -
9) Open FinalBig and select Edit>Add New Directory (near the bottom of Edit list) and then navigate/browse to your MyMods>My Moded Ini Uncompressed>Data (just highlight the data folder) and click ok...it'll take a short while but it'll load up your modded ini into FinalBig.
10)In FinalBig goto File>Save As and navigate/browse to your MyMods>My Moded Ini folder and name your big file ini.big and click save.
11) you now have your new ini.big file in that folder that you can copy to your game directory where the original is (make sure you have a back up first...I always stress this as it is very important).
12) once the ini.big is over-written with your new ini.big your game is moded....you'll then just need to fire up the game with the normal shortcut. At first, depending on various factors such as how much was moded, you might get a game.dat error or something (the yellow warning box thing)...try again, second try might say game is already running, but 3rd try should work. Could be my dvd drive needs a smack with a sledgehammer tho....lol.
If there's anything wrong with any mod you've applied that causes code conflict you'll likely get the eroor box with a red cross in it....that means you need to alter your mod and correct the errors or switch back to a previous ini.big that last worked.
I hope this helps.