My dad had this issue on his machine. For some reason, it just started asking him to change his password and gave him a deadline to do so. He was puzzled because he had never entered a password to his account. The deadline came and he was totally locked out. He kept putting in the password he uses most often, and it would not let him in. I think it's probably because XP was confused when he didn't enter an initial password.

I was able to log in using the administrator account and the normal password, and I changed his account to never ask for a password and, more importantly, to never change the password. You may want to do this too, Phil, if you ever get back in.