hey ptreves, you have been installing a nd creating database for a long time now if I remember right. And usually the first thing anyone creating a database encounters is the init.ora file which you still seemed to have never seen. That's really bad froma dba point of view.
That is the file which defines most of the oracle parameters for your database.
Like Ken mentioned, you will find it in $ORACLE_HOME\dbs most probably as a link or you may find it under the \pfile directory wherever that has been created for you when you created the database using the database configuration assistant.