I had XP Pro at a job, and I could temporarily lock my computer so that only myself or an administrator could log in to unlock it. With my own installment of XP Pro, I don't seem to have that option. If I hit ctrl-alt-del, I get task manager, with other options, but I can't lock the workstation. I can only logout, which still allows another user to click on his login name and log in. What if I want no one else to be able to log in without my own or an administrator's password?
That computer at work was configured so that I typed my user name upon login. Maybe that is related to the difference. Stupid Wndows "features".