actually removing a user

[Mike McMullin]

  I've removed a user or two on my laptop (didn't expect them to use the
system again, my bad, and removed their /home/deleteduser directories.
I want to re-add the user with their old log-in names and create
new /home/<addeduser> directories, but 9.04 complains that the user
exists, even though /etc/passwd and /etc/shadow and /home/ tell me that
they aren't there.  What am I missing and how do I actually, totally
kill a user account to the point that it can be re-created as a new
account?