ADMINSTRATOR AND ALL USERS DELETED

My laptop was doing fine yesterday. Today when I turned it
on, I got the Windows XP blue screen that said "Choose a
use to log on." The problem is there are NO USERS!!! NONE!

I hit Ctrl+Alt+Del twice and got the logon box, but
nothing works. I even logged on in Safe Mode, where I was
told I could log on as Adminstrator with the password
blank and it didn't work.

I don't know a lot about XP ( I haven't been using it very
long), but I have not set up any passwords or separate
users. The tech support guy told me that "It is impossible
for the adminstrator to be deleted, but yours is gone."

Is my only option here to restore my system????? Please
say no. I do have things backed up for the most part, but
WHAT A HEADACHE!!!!!!! Thanks for your help!!