Haro~! Here is how to unlock all starting factions. Some of you know it already but there is so far no thread about it so I am putting it here. I have tested it personally and I assure you it works.=)
1. Go to this link. http://www.strategyinformer.com/pc/mods/napoleontotalwar/mod/category2.html
2. Scroll down and download the modded files that will allow you to play as various nations. There is a total of 6 files. Here is the list.
Austria_ Ottoman Empire
Great Britain_ Spain_ Portugal_ Netherlands
Denmark_Sweden_Prussia_Russia
Oldenburg_ Mecklenburg_ Saxony_ Hessen
Naples_Sicily_Papal States_Sardinia
Italy Kingdom_Wurttemberg_Swiss Confederation_Bavaria
3. Unzip them using Winrar or similar programs.
4. Go to your folder called C:Program FilesNapoleon - Total Wardatacampaignsmp_eur_napoleon.
5. Find and back-up your original scripting.lua and startpos.esf files. Backing-up means to make a copy of and store it in a safe place for future uses. You will need these files if anything untoward happens which I will assure you it won't.
6. Replace your original scripting.lua and startpos.esf files with the ones you you unzipped.
6. Enjoy the changes! Just choose Single player --> Campaign of the Coalition, and you can play as those nations mentioned in the downloaded file name.
NOTE* There is a limit of maximum number of factions that can be shown on the Campaign start menu (four to be precise) so you can't have all the factions at once. Here is a 'trick' to resolve that. Go ahead and do the replacing of scripting.lua and startpos.esf files with the first patch of files--lets say it is (Great Britain_ Spain_ Portugal_ Netherlands), start with each of those 4 nations and SAVE those states separately.
Then replace your scripting.lua and startpos.esf files again with another patch of modded files--lets say (Oldenburg, Mecklenburg, Saxony, Hessen). Start with those factions and immediately save each one of them separately.
Rinse and repeat until you saved all the factions you want to play as in the Campaign. Now finally change back the scripting.lua and startpos.esf files with you original one you backed up--just incase.
Anytime you want to play, just load the corresponding save state of that nation and you can play as that nation, even if that faction is not on the Campaign start menu. Here is a sample picture of how I did it.
<a href='http://forums.heavengames.com/redir/http://img185.imageshack.us/img185/797/20100902014308listsofna.jpg' target=_blank>[JPEG, (211.50 KB)]</a>
Uploaded with ImageShack.us
At the last, sincerely I hope your had managed to follow these very simple instructions and I hope you are as thrilled as I am in starting out as those new factions and find them as challenging (some factions start with just 1 building--ONE!) but not as disappointed with unit selections since they don't vary as much in my opinion (some factions have only 4 types of infantry and only one cavalry--Portugal). Well, that's N:TW for ya..just muskets and wigs and nothing much else. And beards.
PS: I dearly hope the upcoming Shogun2 : Total War will not be the same (who am I kidding, it will be just the same with exactly the same Ashigarus and Samurais available to every faction-- Still, Takeda is badass). East Asia: Total War is what is really needed. =P

Windows 10 microphone delay. [This message has been edited by K Masashige (edited 09-01-2010 @ 11:57 PM).]

Whoah, hadn't noticed this before. Good guide K Masashige. Would you mind if I make this into a guide for the guides&articles section? I'd start by moving it to the g&a forum so people can offer suggestions for improvement and after that I'd publish it on the frontpage. All credit goes to you ofcourse.