I believe this KB will guide you in the correct direction. http://support.microsoft.com/kb/278875
/aaron From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Antonio Aranda Sent: Wednesday, December 06, 2006 3:12 PM To: ActiveDir@mail.activedir.org Subject: [ActiveDir] AD with mixed DC I have an AD domain with 2 2k domain controllers. I want to add a thirds domain controller that has a 2k3 os. I know there is something that needs to be enabled or disable before having an AD with mixed DC. What do I need to do before adding the third DC? Thanks Antonio Aranda Network Analyst UT-Permian Basin 432-552-2413