Unknown User at log in

Archived from groups: microsoft.public.windowsxp.general (More info?)

When starting my computer I get the login screen with "Unknown user" in the
user name field. I am trying to get rid of this but can't find anyway to
eliminate it. If I try to log the user out it locks the computer and I must
go through the login to get it back on line. There is no user (Control Panel
- User Accounts) listed as unknown. I have tried logging in as the admin then
shutting down the unknown user but with the same result. Any ideas on how to
rid myself of this nuisance.