"Service Pack 2 cannot be removed easily, due to system table changes the service pack requires for maintenance. To revert to a build before SP2 was installed, you must reinstall SQL Server 7.0 and, if required, apply SP1 to the installation. Before you reinstall SQL Server 7.0, detach your databases on SP2 and reattach them after you reinstall SQL Server 7.0 and SP1. For information about using the sp_attach_db and sp_detach_db stored procedures, see SQL Server 7.0 Books Online. As with any new installation, you must re-create the necessary logins. You must also re-create scheduled tasks dependent on information in the msdb database, as well as any changes you have made in the model database. If you use replication, you must completely reconfigure replication. "

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q254555