Oracle Database Discussions

Hi all. we are using oracle 8.1.6 on windows-2000 with 2gb ram. we facing
ora-12500 listner failed to start a dedicated server.
error and for this we made certain changes. we also added a parameter in sqlnet.ora at server side sqlnet.expire_time=10.. for automatically killing inactive sessions but it did not helped and many sessions remain in v$session. i wana know what should we do to kill inactive sessions. because i think when the sessions reach more than 300 then we face problem of listner failed. thanks for u'r valueable comments in advance as well.
best wishes
muhammad mohsin chattha