Oracle 7.3.4.1.0 user password expiry issue.

In Oracle 7.3.4.1.0 I am facing a problem of account expiry every day I have to change the password.

ERROR: ORA-01017: invalid username/password;

I have also check the default profile of the users

PROFILE              RESOURCE_NAME                       LIMIT
-------------------- ----------------------------------- -----------------
DEFAULT              COMPOSITE_LIMIT                     UNLIMITED
DEFAULT              SESSIONS_PER_USER                   UNLIMITED
DEFAULT              CPU_PER_CALL                        UNLIMITED
DEFAULT              LOGICAL_READS_PER_CALL              UNLIMITED
DEFAULT              CONNECT_TIME                        UNLIMITED
DEFAULT              PRIVATE_SGA                         UNLIMITED
DEFAULT              IDLE_TIME                           UNLIMITED
DEFAULT              LOGICAL_READS_PER_SESSION           UNLIMITED
DEFAULT              CPU_PER_SESSION                     UNLIMITED

Suggest if there is anything else I have to check in Oracle 7.3.4.1.0???