You cannot uninstall any SPs associated with Exchange (excerpt from SP2 release notes - "Important: After an Exchange Server service pack has been installed, it cannot be uninstalled. If you must revert to the version of Exchange Server that was running before the service pack was installed, you will have to remove Exchange Server from the computer, reinstall Exchange Server, and then restore the Exchange databases from a backup"). Here is the actual URL:
http://download.microsoft.com/download/f/b/5/fb5c54af-fe5c-48e9-be97-f9e8207325ab/Ex_2003_SP2_RelNotes.htmRegards.
~coolsport00
