if you're on unix, go to $ORACLE_HOME directory, then into dbs directory. there'll be a file there for each SID (database) with a file name initTHE_SPECIFIC_SID_NAME.ora
there'll be one entry for each SID/database (if it's not specified as * = ALL) in /etc/oratab.
On windows, go to oracle insallation directory, then database directory...there'll be a initSID_NAME.ora for each SID/database. There'll be a windows service for each SID, with a name like oracleserviceSID_NAME.
the hardest line to type correctly is: stty erase ^H