Script to identify tables without Primary Key

SELECT name
  FROM sysobjects
 WHERE xtype='U'
   AND objectproperty(object_id(name),'TableHasPrimaryKey')= 0
 ORDER BY 1


or

USE DatabaseName;
GO
SELECT SCHEMA_NAME(schema_id) AS SchemaName,name AS TableName
FROM sys.tables
WHERE OBJECTPROPERTY(OBJECT_ID,'TableHasPrimaryKey') = 0
ORDER BY SchemaName, TableName;
GO