Exchange 2000 SP1 Fails

Have a SBS 2000 server. Have SP2 for Windows 2000. Tired to install SP1 for exchange and get error telling me that most current SP1 is on.
Norton Anit Virus for Exchange 2.5 software require SP1 for exchange and when I try to run it tells me I don’t have it.
ALready went through with Microsoft to uninstall and reinstall Exchange 2000.
Any ideas?