Administrator account automatically logs in on startup

I have XP Pro at home. I have set up individual accounts
for each family member. However, when the computer is
rebooted, the Administrator account automatically logs
in. You have to manually log out of that account, then
you get the usual 'welcome' screen with only the family
names on it (not Administrator). I'd like to stop
Administrator from automatically logging in on bootup.
It's a huge security hole right now, as anybody can log
in just by rebooting (and as the most powerful
account!!!).

btw - the administrator account does have a password - it
just doesn't seem to require it for reboots! I don't
want to have to disable it - but I do have administrator
privileges on my own account - which is also password
protected.