If you mean to transfer data. You best of adding the new server as a domian controller, ensuring that all the user accounts are migrated. Then disconnect the old server and run both for a while to ensure that the new server is working at full functionality.
Unless you are using the same licence for W2kS, then do as above, then reconnect the old server as a back up.
In my opinion Windows 2003 Server is the King.
Of course update ERD and backups before carrying out any major work on a server.
I believe you need to do a DC Promo in there somewhere too, because if you have emulation turned on for the Primary Domain Controller (things that older Windows wants to know about), you need to do the promo thing to migrate the catalog server, and any PDC emulation.
There are also software packages available to assist in your migration.