'ORA 12542: TNS: address already in use' error

How do I resolve this error please:

'ORA 12542: TNS: address already in use'. OraOLEDB error 80004005

The Listener configuration file, LISTENER.ORA contains an address entry that may look something like this:

(ADDRESS = (PROTOCOL = TCP)
           (HOST = dbserver.mycompany.com)
           (PORT = 1526)
)