Ed,
I get confused about the domain remaning options:
Your answer to T McNutt: Since your're in a coexistence scenario you'll need to do more that remov Exchange 2007 before the domain rename.
Your answer to jwdberlin: Since you have already installed Exchange 2007 into the organization containing Exchange 2003 (or if you have already run the Exchange 2007 /prepare setup switches), you cannot perform a domain rename even if Exchange 2007 servers are removed from the organization.
In a coexistence scenario with Exchange 2000/2003: is it possible to rename an AD domain after removing Exchange 2007 Servers included new Active Directory objects created by Exchange 2007 setup?