Oracle Listener

Are you starting up the listener using SQL or Enterprise Manager. If its SQL, then you need to export the lsnrctl parameter along with other start up parameters. In EM, you search for listener and start it up.
If you haven't created a listener, use the Database configuration assistant DBCA to create one and remember to specify the name of the database the listener will 'listen' on.

Hi, you didn't mention the OS,anyways I will write for both OSes.
Normally if you are running the OS on your PC,I don't think you will need the Listener.The listener enable your database to be able to listen/accept connections from external networks.
Okay for Linux first:
As I said earlier you don't really need the listener unless you ofcourse work for a company.
Okay,on a terminal type
# lsnrctl start
that should start your listener,
you could type
# lsnrctl status
for you listener status
lsnrctl is the name of your default listener(It could be anything)
ok,if you receive any error(s),check your  typing
# netmgr
on your terminal to start Net Manager ,try and locate the listener tab and create one.
Mind you,you could start your EM without the listener,if you are not expecting any connections.For Oracle 10gr1 check under the shutdown tab in the EM homepage.
OR
look under Administration.

okay for Windows.
I think windows automatically starts the listener for Windows.press ctrl+alt+del and go to task manager,then select the processes tab,try looking for anything lthat resembles lsnrctl or any similitude.If you find means it already active,no need to start it but if otherwise.
just go to command prompt and repeat the above processes as for Linux.
Not really familiar with Windows but under the Installation for Oracle check for Net Manager and create a listener.
I hope you understand any of this jargons.
Then please try posting any of the error(s) you might get.
Hope any of this helps.