Standard User Password not saved

Hello

I've recently upgraded from XP home to Vista Premium. I've set up an
administrator account and four separate user accounts. The problem I have had
is that one of the user accounts did not ask for a password when logging in
although a password had been set and applied to this account. Slightly
worried now that this might happen with the Administrator account for obvious
reasons!

Any help, reasons or a fix for the problem greatly appreciated.