You're not logged in as 'root' if you login with 'pi'.
If you were, you did not have to put 'sudo' in front of the 'halt' command. Sudo gives you root permission for the command/program you start with it.
How to delete your own user:
Login as pi, and issue 'sudo userdel -r <name>' and that should fix it. But you can also change the password of the user with 'sudo usermod -p <newpassword> <username>'. (when being logged in under 'pi').
If you make a new user, and you want that one to be able to issue 'root' commands, the user should be added to the sudoers group: 'sudo adduser <username> sudo'
With 'cat /etc/passwd' you get the whole list of users of the (and there are a lot of user for all kind of services, not actual 'user' accounts).
I hope that helps you...
Last edited by stijn.ghesquiere
on Wed Jan 09, 2013 7:38 pm, edited 1 time in total.