HELP!! Logon and Local Users and Gropus Issues

I have basically two problems:

1) I have a laptop that I added to my home network. The
workgroup name is NEWGROUP(in caps).The laptop is used by
my daughter at school and is part of a wireless lan
network. My network at home is not wireless and when I
changed the name of the workgroup on her laptop form
WORKGROUP to NEWGROUP and restarted her password did not
work for her username. So now we are unable to logon to
her laptop at all.

2) Both of my home computers do not show local users or
groups node in the Computer Management window under
Administrative Tools. I have more than 2 users on both
computers. Also do not see the Administrator user unless
I am in Safe Mode. In normal mode only see the user that
I set up in the User Accounts window.

Those are the two issues that I have been unable to
solve. The laptop is using Windows XP Professional and
the other two computer are using Windows XP Home Edition.
Hopefully someone can give me a some help with both or
either of the two problems outlined. Thanks everybody for
your assistance or advise.
..