Log on Oracle: SQLPlus - problems

Installing on Win XP Pro :
Oracle 9i Lite 5: trying to log on with SQLPlus Release 8.1.7.0.0 gives: "ORA-12560: TNS: protocol adapter error" or "ORA-12541: TNS: no process listener";
Developer 2000: trying to log on with SQLPlus Release 3.3.2.0.2 gives: "ORA-03121: no interface driver connected - function not performed".
What I'm doing wrong ?? I haven't been working with Oracle for a long time, and even then with already installed and configured Oracle products and didn't had such problem.
Yeah I'm rather a beginner now...

First check your Orcale service is on or not , goto control pannel then goto services then try to find out OracleService<databasename>, if you find it then turn it on, If you dont find it then create new service to connect with database.


Regards