Login Problem to Oracle 10G (SQL Plus)

How to do it?

1. Logon to the database using SYSTEM or SYS account 
2. Unlock the account alter user <username> account unlock; 

Example: 
SQL> conn scott/tiger@oradb13 
ERROR:
ORA-28000: the account is locked 

Warning: You are no longer connected to ORACLE. 
SQL> conn system@oradb13 
Enter password: ****** 
Connected. 

SQL> select username, account_status from dba_users 2 where username = 'SCOTT'; 


USERNAME                 ACCOUNT_STATUS 
-------------------------------------------------------------- 
SCOTT                          EXPIRED & LOCKED 


SQL> alter user scott account unlock; 
User altered. 
SQL> select username, account_status from dba_users
2 where username = 'SCOTT'; 


USERNAME                 ACCOUNT_STATUS 
-------------------------------------------------------------- 
SCOTT                          EXPIRED 


SQL> conn scott/tiger@oradb13 
ERROR: 
ORA-28001: the password has expired

Finally

1. Close Sql Application
2. Reopen The application
3. A screen will appear to change password 

Changing password for scott 
New password: ***** 
Retype new password: ***** 
Password changed 
Connected. 
SQL>

Ready to Work...