Database diagram support objects cannot be installed

To resolve this error:
Database diagram support objects cannot be installed because this database does not have a valid owner.
To continue, first use the Files page of the Database Properties dialog box or the ALTER AUTHORIZATION statement
to set the database owner to a valid login, then add the database diagram support objects.


In SQL Server Management Studio please do the following:

Right Click on your database, choose properties
Go to the Options Page
In the Dropdown at right labeled "Compatibility Level" choose "SQL Server 2005(90)"
Go to the Files Page
Enter "sa" in the owner textbox.
Hit OK