press ctrl/alt/del and see what happens
if the above doesn't work
try loading in safe mode by tapping F8 during bootup
get back to us with the above.
Last night I installed the latest XP update, and now when I try to start Windows the user list does not appear on the opening screen. The only thing I can do from the screen is shut down or re-start the computer. System Restore has not helped. Any ideas?