ORA-12571 and ORA-12560

I've installed Oracle 8i in XP platform. I've tried to connect to my database, but after login in, i receive errors ORA-12571 (writer packet failure) and ORA-12560 (Protocol adapter error).

Most of people tell me that maybe I configure in bad the way the listener.ora and tnsnames.ora files. But I don't think so: I need help, please.
Thanks in advance.

TNSNAMES.ORA # TNSNAMES.ORA Network Configuration File: C:\Oracle\Ora81\NETWORK\ADMIN\tnsnames.ora

# Generated by Oracle configuration tools.

ORCL =     (DESCRIPTION =
(ADDRESS_LIST =
            (ADDRESS = (PROTOCOL = TCP)(HOST = pfe-2kznt32b8ki)(PORT = 1521))

        )

    (CONNECT_DATA =
(SERVICE_NAME = ORCL)
    )

)

LISTENER.ORA # LISTENER.ORA Network Configuration File: C:\Oracle\Ora81\NETWORK\ADMIN\listener.ora

# Generated by Oracle configuration tools.

LISTENER =     (DESCRIPTION_LIST =
(DESCRIPTION =
            (ADDRESS = (PROTOCOL = TCP)(HOST = pfe-2kznt32b8ki)(PORT = 1521))

        )

     (DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = pfe-2kznt32b8ki)(PORT = 2481))

    )

)

SID_LIST_LISTENER =     (SID_LIST =
(SID_DESC =
            (GLOBAL_DBNAME = ORCL)             (ORACLE_HOME = C:\Oracle\Ora81)

            (SID_NAME = ORCL)         )

    ) Received on Wed Jan 15 2003 - 14:04:42 CST