Change of Windows XP password changes Outlook 2003 password

Hello group.

My users are experiencing the following problem: Everytime they change their
Windows XP local user password (which expires every X days) the next time
they try and open Outlook 2003 it prompts them for a password (their outlook
2003 passwords are saved).

A couple of points:
We are not using an AD
We do not used Exchange, rather a POP/SMTP mail server.

As far as I can tell, Windows is trying to be 'helpful' and change their
Outlook password to match their new Windows password, as a result of which
the users are blocked from accessing their emails.

Am I correct in my assumption, and if so, does anyone know of a way to turn
this off?

Thanks,
Alex