Modding tools?

[DoctorFosstus]

What do I use to edit the game files? when I try to open nation files, my computer does not recognize the file format.

[Agrajag]

Go into your dominions 3/doc/ folder, in there you should find a modding guide.
Modding is done, by the way, using any old text editor and saving to .dm files.

[llamabeast]

Yep, you want to open it in Notepad or Wordpad or some such.