I'm not sure what the problem is. Regardless of using the welcome screen or not, you can have a blank password. If you use a welcome screen and click on an account with no password, it logs in. If you don't use the welcome screen, just leave the password box blank and log in. If it doesn't allow you to log in, then the password has been changed.
If Owner has no password, just tick the Use the Welcome Screen" option in User Accounts>Change the Way etc. Administrator won't show up and the welcome screen will just show Owner and you simply click on the icon. Check first that Administrator isn't an account with that name as opposed to the system Administrator.
Windows updates (WinXP) undo personal settings (solution from ""xpforums.com")
ie, Windows updates adds a new user-account "asp.net" which must be disabled (or deleted)
then bypassing the login screen can be set.