how to migrate to windows 2003 server

Hi,
We have two NT servers. One is file/printer(PDC)server.
another is Exchagne server5.5.(BDC)
Here is my question.
I am getting new server with windows 2003 with exchagne server 2003.
How can I migrate all users accounts in NT and Exchagne server accounts.
I foung there is a migration tool.
I want to make sure is it works.
What is the best solution

Guidence please.