In sql 2005/2008 you can use ALTER DATABASE statment easily modify database name.
ALTER DATABASE Northwind MODIFY NAME = Northwind _Test
--The database name 'Northwind _Test' has been set.
Back up the master database after you rename any database.
ALTER DATABASE Northwind MODIFY NAME = Northwind _Test
--The database name 'Northwind _Test' has been set.
Back up the master database after you rename any database.