I have an exchange 2003 server which I need to replace. I have the new server and am ready to get it up to speed but I need to find out the best way of replacing the old server with this server and of course with the least amount of downtime.

You're going to have to deploy a new mailbox/exchange 2003 server in your org. Then once that server is up and tested move the mailboxes from the first server to the new server. Then decommision the old server.There will be down time when you're moving the mailboxes.The other thing you will need to do is change any DNS/MX records etc depending on how you have your mail routing configured. BP

http://support.microsoft.com/kb/822945/en-us, but this would cause downtime.The previous post would work if the server only hosts mailboxes and there are other servers that host the other things like public folders or connectors.

Further references: Exchange Server Move Method How to remove the first Exchange Server 2003 computer from the administrative group

Thank you everyone for your insights and help on this. Doesn't sound like the quick task I was hoping it to be. Having installed a lot of first exchange servers into a domain, this is the first time I had to go back and replace one. The url's that were listed are also very insightful. Thank you again.