Vista Business - Logon Issue.

I am a complete newbie to Vista and might be doing something completely
wrong which some of you more experienced guys will probably see as a
stroll in the park, so here goes...

I have a HP Compaq 6720s laptop with Vista Business installed. It will
be used on a school network and has been configured to run on the admin
domain, by going to system properties then computer name, selecting
change, assigning the computer name, then the domain name (from
workgroup to domain).

The local profile has been set for each user by going to My Computer
and right clicking the icon, then selecting manage, selecting local
users & groups, users, then groups and ensuring admin access is
available.

After a reboot prompted by setting the domain to admin, I end up with
the login screen and select Ctrl+Alt then Del, but then something
different from the norm happens...

Upon entering the username "administrator", the domain changes from
admin to local machine before I get a chance to enter the administrator
password. There is a prompt when this happens and the only way I can get
into the administrator account is as follows...

Username: admin\administrator
Password: <administrator password>

I feel sure I have missed something somewhere and would appreciate any
help you can offer to put me back on the right path. Cheers in advance.


--
Techy