I only have 1 NT 4.0 member server and everything else is Win 2000 Server except for the DC which is Win 2003 running AD. I have another DC, but that is Win 2000. I have Exchange 5.5 running on a win 2000 server. Are there any problems with me switching to Native mode? Do I have to have all WIn 2K3 DC's before switching to Native Mode or is that not a factor since it is win2k vs win2k3 and not win nt 4.0?