I need to uninstall 1 of two Exchange 2003 servers and reinstall it. We have Exchange 2007 but have retained two Exchange 2003 servers. The server I am rebuilding does not hold any roles. I moved the mailboxes off to the other Exchange 2003 server first. Any issue with re-installing a single Exchange 2003 server with an extended schema for 2007 as long as I install it back into the existing Exchange 2003 administrative group?

It should be fine.

Agree with Andy, should be fine If it’s the first exchange 2003 server, please see the KB below How to remove the first Exchange Server 2003 computer from the administrative groupJames Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com