I have my application running in Visual Studio 2005 with ODP 10.2.0.2.21 and Oracle Client 10.2.0.1.0 (both 32 bit version). The machine I am using is a 64 Bit machine running the 64 bit version of Microsoft Server 2003. When I run my application through the IDE, it runs without any problems. I can also connect to the database through SQL Plus. But, when I create the installation package and install the application on the exact same machine, I start getting the following error: "Oracle.DataAccess.Client.OracleException ORA-12154: TNS: could not resolve the connect identifier specified at Oracle.Client.OracleException.HandleErrorHelper...." The tnsnames is correct since I can connect through the IDE and SQLPlus and I have checked the GAC and the Environmental Variables and they are all correct. I only have the Oracle Client and the Oracle ODP installed. There are no other versions of oracle on the machine. The machine was also rebooted after the ODP was installed. Any idea of how to fix this?