Working with SQL Server 2000 Diagrams
SQL Server 2005 database diagrams and SQL Server 2000 database diagrams are created and rendered differently. Because of these differences, SQL Server Management Studio cannot work with SQL Server 2000 diagrams. Use SQL Server 2000 Enterprise Manager instead.
When a database that contains diagrams is upgraded to SQL Server 2005, the diagrams will be upgraded when the diagrams folder is first opened.
To upgrade database diagrams, the user must be a member of the db_owner database role, and upgrade the database must be in SQL Server 2005 compatibility level. If the database is set to the compatibility level of an earlier version, you might receive the following error message:
"Database diagram support objects cannot be installed because this database does not have a valid owner."
To continue, use Management Studio or sp_dbcmptlevel to set the compatibility level to SQL Server 2005.