ORA-12541 error while connecting to oracle express edition 11g My oracle express edition was working some months earlier. 

I dont know what i changed in the system, now I could not connect to it. I tried logging in from sqlplus as sysdba and altered the accounts to unlock, grant connect and resource privileges but I couldn't connect to database through sqltool.

I checked the listener.ora file where the host was Rajan. Ping on Rajan is working(pointing to localhost).
TNS-12541: TNS:no listener

Error message is self-explanatory, the listener is not running, so start the listener with "lsnrctl start".
Since you are on Windows, it runs as a service, so you can start the service itself.