The only times I've seen this occur is when the computer is
running XP Home Edition and it's been configured to
automatically logon the built-in Administrator account. With XP
Home Edition, the built-in Administrator account can only be
accessed when the computer is running in Safe Mode.
When you see the error message, there should be an OK button.
Hitting the OK button should take you to the Welcome Screen
which will allow you to log on with your user account. Once
logged on, you should run control userpasswords2 again and put
the check mark back in the box on the Users page. Reboot and
see if the welcome screen is displayed.
If you're still unable to fix this problem, you can try booting
into Safe Mode.
Restart your computer and start tapping on the F8 key.
Keep tapping F8 until the Windows Advanced Options menu is
displayed.
Use the up arrow key to highlight Safe Mode and hit the Enter
key.
Hold down the Shift key until you see the Welcome screen
displayed.
Click on the icon for your user account.
Once the computer has booted into Safe Mode, do the following:
Go to Start -> Run and enter control userpasswords2 in the Open
box.
Click OK.
On the put the check mark back in the box next to "Users must
enter a user name and password to use this computer".
Hit the Apply button.
Now go back and remove the check mark.
Hit the Apply button.
In the box that pops up, replace Administrator with the name of
your user account.
Enter your password, if any, twice.
Click OK.
Restart your computer and see if it now logs on your account.
Good luck
Nepatsfan
(e-mail address removed),