TNS_ADMIN

I installed Oracle SQL Developer, and it worked fine. Then on another day, I installed Oracle XE database. It somehow changed my settings so that I no longer see the entries in tnsnames.ora. I can'd do a tnsping in dos either, it showed a different SQLNet.ora.

After searching online, I found that I need to set the enviroment variable: TNS_ADMIN, and set it to the folder which contains my tnsnames.ora. After that's set and SQL Developer restarted, I am able to see all the entries.