Possible two log-ons for one user?

I boot WinXP Pro with a password. I am the only user and also the
Administrator with the same password.
It now looks like that there are two users (i.e., two logons). The reason
is that when I log on the windows, I get A screen. When I reboot the
computer later, I get B screen. Both A and B screens are very similar but
two desktop icons are missing in one of the screens. I am quite puzzled
about this observation. My question is how to confirm that there are two
users (or logons) for one person, and if so, how to get rid of one of the
two logons.
Jorge