invalid username / pasword even if I change the password at server level

Hi experts.Database version 9.2.0.7.
invalid username / pasword even if I change the password at server level
All users even Sys is happening this.  I cannot enter with any password.
System description, taken inside the server connecting /as sysdba:
How to solve this?
SQL> select username,account_status,ex

piry_date,profile,created,external_name from dba_users where username='SYSTEM';

USERNAME                       ACCOUNT_STATUS                   EXPIRY_DA
------------------------------ -------------------------------- ---------
PROFILE                        CREATED
------------------------------ ---------
EXTERNAL_NAME
--------------------------------------------------------------------------------
SYSTEM                         OPEN
DEFAULT                        20-JUN-07




SQL> desc dba_profiles
Name                                      Null?    Type
----------------------------------------- -------- --------------------------