Lost All User Accounts

I am working with XP; I went into the control panel and clicked on Adminstrative Tools. then went to Computer management & clicked on Local Users & Groups, followed by “Users”.

I then right clicked on Adminstrator and clicked on ‘set password’ and then entered one. Afterwards, I logged off & turned the computer back on. The only user option that I now have is the guest user. There is no other choice. I lost ALL of the other user accounts from the log in screen.
Having said that, my only choice is to click on the ‘guest account’ to log on and, with that, I cannot get into any type of admin under computer management.

I need to get all of the user accounts back; can anyone help??

Thank you in advance!