I would try logging into single user mode and delete the file /etc/sysconfig/firstboot this will trigger the "first boot" dialog and you can create a new user there.

Logging into singleuser-mode:

Add the word "single" without the "'s to your kernel string via the boot loader

On Sun, Apr 21, 2013 at 10:15 PM, Archie Kidd <archkidd@gmail.com> wrote:
I have installed Fedora-18-i686-Live-Desktop.iso on a bootable usb
using Universal USB Installer v 1.9.3.1. in order to try it.  (I am currently using Mint 14.)

Program installs and opening screen shows the logo and top icon bar and:
'Sign in' (greyed out)
'Not listed?'

Selecting 'Not listed' produces a request for 'Username' with a box
to fill in, and 'Cancel' or 'Sign in'
Everything I try on the username produces 'Authentication error'
and returns to sign in screen.

Can anyone help me get to the program?

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