If you have an XP Home machine you may not need
to use it. In XP Home, boot the computer into Safe Mode. Do this by
repeatedly tapping the F8 key as the computer is starting up. This will
get you to the right menu. Navigate using your Up arrow key; the mouse
will not work here. Once in Safe Mode, you will see the normally hidden
Administrator account. The default password is a blank.
In XP Pro, you do not need to go into Safe Mode. At the Welcome Screen,
do Ctrl-Alt-Del twice to get the classic Windows logon box. Type in
"Administrator" and whatever password you assigned when you set up
Windows.
http://home.eunet.no/~pnordahl/ntpasswd/
If you reset the built-in Administrator account's password in Home or
have Pro and don't remember the password, use NTpasswd to change the
built-in Administrator account's password to a blank.
However, if your wife's friend was so untrustworthy I think I'd back up
the data, wipe the machine and clean-install Windows. Who knows what
else she did? Be sure your machine really belongs to you and not her.
http://michaelstevenstech.com/cleanxpinstall.html - Clean Install How-To
http://www.elephantboycomputers.com/page2.html#Reinstalling_Windows -
What you will need on-hand