By default, Windows XP is set up with passwords which will expire after 42 days. 14 days in advance, Windows will start warning you of this fact. If you do not want your passwords to expire:
- Go to Start > Run and in the Open: box type control userpasswords2
- Select the Advanced tab in the User Accounts window
- Press the Advanced button below the Advanced user management header
- Select Users in the Local Users and Groups
- In the right pane, right-click the user name for which you want to change the setting, and select Properties
- On the General tab, check Password never expires
- Click Apply and OK (all the way out)