XP won't let you delete all admin accounts so this should be some relief!
There will be a master account with user name "Administrator". I hope you
know its password. XP's installation prog would have asked for this password
from you. To login as this account, at the Welcome screen press ctrl-alt-del
but tap the del key twice while still holding the ctrl-alt keys. This will
present the a login screen. Type in the user "Administrator" (no quote
marks) and its password. Now you can create another user admin account.
However, you will still have a problem accessing the folders that were owned
by the deleted account (Access denied msges). You will need to change
ownership as follows. Rt click a folder you want to change and goto
properties/security/advanced/owner and change the owner there.
Good luck.