Environment: - Oracle 10g database over a windows 32bit 2003 server - SQL 2005 database over a windows 32 bit 2003 server. I am trying to connect the above databases through heterogeneous services. I have updated the following files: TNSNames.ora, Listener.ora and hs.ora. When performing a test connection from SQL developer, I get the following error - ORA 28500 - indicating that the login for SA user is incorrect. I also tried using another authenticated user that has rights to the database. I can successfully connect with SQL 2000. Has anyone experienced such a problem before?