Built three identical Win7Pro systems. All three have SQLNET 32-bit. All three have PL/SQL 8.0.2. All three have identical copies of TNSNAMES in the C:\...admin\ folder of Oracle. However, two of the three connect using the SQL login and PLSQL GUI login but the 3rd will only connect at the SQLNET login (all three PCs are on the same VLAN - all three users have identical hardware as well). Confirmed that the TNSNAMES.ora file was in the right location on the failing system and also added the TNSNAMES.ora folder path to the PATH statement via the Environment Settings. Confirmed PATH statement via PATH command execution. Also rebooted system. Checked permissions on the entire path of TNSNAMES file. Is there a "config" file within PLSQL that can be examined to see where it is looking for the TNSNAMES file?