Alter Database Authorization in SqlServer 2005

"Database diagram support object can not 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 object "

I have resolved the above issue few days ago by alter database authorization. According to MSDN the Alter Authorization syntaxt is

ALTER AUTHORIZATION
  ON [  :: ] entity_name
  TO { SCHEMA OWNER | principal_name }

 ::=
   {
       Object | Type | XML Schema Collection | Fulltext Catalog | Schema
   | Assembly | Role | Message Type | Contract | Service
   | Remote Service Binding | Route | Symmetric Key | Endpoint
   | Certificate | Database
   }

my SQL statement was

ALTER AUTHORIZATION ON Database::databasename TO username;

Hope it will help you. Enjoy!