I have Windows 2000 Pro.  While visiting my son's house with my work
laptop, I was changing from a domain to a workgroup to access his
broadband connection.  Under the users tab, I accidently check the box
that says assume the following user will always log on (or something
similar).  The user was localadmin.  When I rebooted, I only have the
option of logging in as localadmin for which I do not have the
password.  Is there any way for me to change this back to the original
setting (prompt users to log in) so I can log on normally with my user
name and password?

Wether or not you checked the assume following user will always log on
is not a question. Since its set on the workgroup and there is only 1
local user (the administrator) you will need to sign on that name and
change it back to domain access so it can use cached domain
names/passwords.  Without knowing the password, there is only 1
solution, to reset or change it.

*** http://home.eunet.no/~pnordahl/ntpasswd/

That website contains a peice of software that will allow you to boot
from its cd and change/reset the password for any local user on the
system for any Windows NT/2000/XP installation.