We have heard from a number of customers asking if the SQL Server 2000 JDBC driver will work with SQL Server 2005. Unfortunately, it will not.
If you are looking to migrate an existing SQL Server 2000 JDBC application running on the SQL Server 2000 JDBC driver to SQL Server 2005, we recommend that you download the latest SQL Server 2005 JDBC driver at http://msdn.microsoft.com/data/jdbc and update the existing JDBC application to work with the SS2005 JDBC driver. Once that is working, upgrade the backend SQL Server 2000 to SQL Server 2005. The SQL Server 2005 JDBC driver will work against SQL Server 2000, 2005, as well as the upcoming SQL Server 2008.
SQL Server JDBC Team