Ive recently installed Oracle 10g on my Windows XP and was able to connect. When i did a shutdown immediate and tried to connect again as a sysdba i get an error:

ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

Did a few basic checks like Oracle services, listener and all seems up and running. As im studyin Oracle 10g currently, please explain me in simple language meand guide to what i should do to resolve this problem. Any help is much appreciated!

Below is my TNS, listener details for your reference

TNSNAMES

ORCL =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orcl)
)
)

EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)
===================

LISTENER

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = C:\oracle\product\10.2.0\db_1)
(PROGRAM = extproc)
)
)

LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
)
)
================================

Using 'conn sys@orcl as sysdba
password: sysdba'