Thanks Misty_rain and Thatguy.

Let me clear myself a little bit.

Case 1: two computers A and B. I like to transfer all the users account from A to B in one try.

Case 2: If one user by mistake deletes his account, I want to be able to restore from my backup user table.

Case 3: If in future I have to format my computer, i need all the user account restored

Hope that helps answering.
Cheers