Here's a good HoI2 Editor. Click
here
It's a simple program; you just open the province.csv file with it and everything is laid out fairly simply. You will need to know the province ID number, which can be found in-game (press F12 and then type showid) in the bottom right corner. There's also an online map (
here) which will give you the IDs.
Unless I'm mistaken, Armageddon/Doomsday (not sure which) comes with an easy-to-use editor which allows you to do this and even names the provinces so you don't have to hunt for the IDs. It will be in your Doomsday directory.