ALTER DATABASE OldDabaseName MODIFY FILE (NAME='OldDatabaseName', FILENAME='C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\NewDatabaseName.mdf');

ALTER DATABASE OldDatabaseName MODIFY FILE (NAME='OldDatabaseName_log', FILENAME='C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\NewDatabaseName_log.ldf');

ALTER DATABASE OldDatabaseName MODIFY FILE (NAME = OldDatabaseName, NEWNAME = NewDatabaseName);
ALTER DATABASE OldDatabaseName MODIFY FILE (NAME = OldDatabaseName_log, NEWNAME = NewDatabaseName_log);