I have a replacement server for my PDC/Exchange server being built right now - the replacement will continue to be the PDC. The reason is that I want a 64-bit machine for my upgrade to Exchange 2007. But, I'm anxious to get as much done now as I can so I don't have to rush before I go on vacation. The PDC MUST be replaced and I'd rather have the newer/faster/better machine as the PDC and Exchange server. Can I upgrade my backup DC and two othere servers in the domain to Server 2008, ahead of my PDC?