I'm just consolidating what I found from various other web pages. It's easier to refer to than looking all over the web.
tnsnames.ora file in Windows can be found at:
%ORACLE_HOME%/product/11.2.0/dbhome_1/network/admin
Since I'm no genius in Oracle, I had to look for the ORACLE HOME directory. You would need administrative access to the server or PC since you need to fetch this from the registry.
- Open Start > Run > regedit
- Navigate to HKEY_LOCAL_MACHINE / SOFTWARE / ORACLE / KEY_OraDb11g_home1
- You will find a key ORACLE_HOME and it's value would contain the path