I have installed Oracle8i (product:programmer) on Windows 2000 Professional. When I try to login into SQL*Plus using the user scott and tiger password and giving the host string the company name which I gave when installing the OS, it gives the error: ORA-12541: TNS : no listener. Then it stops. I tried using another host string but it just hangs up.
It sounds like the TNS Listener service on your database server is not running. If you're connecting to a database on Windows, look in the services control panel for a service named "Oracle
If your database server is running on a Unix-based host, you can login as the Oracle user and run "lsnrctl start" to start the listener.