Performing an in-place migration from exchange 2000 to Exchange 2003 is generally an easy task.
Firstly you must make sure that your current Exchange 2000 server is running at least SP3 and that the Server 2000 server OS which is hosting the Exchange 2000 software is running at least SP3.
If these prerequisites are true then all that is left is to insert the Exchange 2003 server CD and run the setup wizard.
Select Exchange Deployment Tools, then Deploy the first Exchange 2003 server, then Upgrade from Exchange 2000 Native Mode.
From here check and perform the first 8 tasks before then doing step 9, the upgrade.
Once this completes restart your server and you will now be running Exchange 2003. It is recommended to install Exchange SP2 from here on.
