Can't get into Fedora 18

Sun Apr 21 20:15:30 UTC 2013

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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