[Alneyan]

So long as you do not play two nations on two different computers on the same turn, it should work, but no promises here. I believe the game checks the key and the computer used to play, and will trigger the key alert if two nations use the same key and different computers.

Playing several nations with the same computer and key is fine, and switching computers should be fine too. You may want to "carry around" your .2h files however, as otherwise you will have trouble connecting to the game from the other computer. The files can be found in the Dominions2\[Game_Name] repertory, and they are the [Nation_Name].2h files; those contain all your orders for the current turn.