Installing Exchange 2003 on Windows 2003 SP1
You may have noticed an error that pops up when you run the Exchange 2003 setup program on a Windows 2003 Service Pack 1 server. The message says: Exchange Server 2003 has a known compatibility issue with this version of Windows. For more information, refer to http://go.microsoft.com/fwlink/?LinkId=37488. To run the program, click Continue.
You should be able to run setup without incident, just make sure that you apply Exchange 2003 Service Pack 1 as soon as you are finished. The document System Requirements for Exchange Server 2003 covers the necessary requirements for Exchange 2003 on Windows 2003 SP1 (which I have linked to previously).
Someone reported to me that they had a problem running forestprep and domainprep from a member server. If this is the case, run the /forestprep and /domainprep options from a domain controller instead. This seems to address the problem.