Doesn't appear possible. You can do NT style PDC and BDC, but not AD. This thread discusses it some
http://www.mail-archive.com/linux-il.../msg48963.html, and the current state of Samba 4 (which is planned to be able to do what you want) is that it is still in Alpha --
http://www.samba.org/samba/docs/FAQ/. There is a chapter on configuring Samda as BDC, but it's complicated (which they say at the beginning) --
http://us3.samba.org/samba/docs/man/...samba-bdc.html. If you dump the 2003 server and do it all with Linux and Samba, then you could, but you won't have some of the functionality of a 2003 Server with AD.