Live user keeps appearing

This is the first time i have used Linux
I have installed linux mint xfce [full install]. It seemed to work ok. After i did the updates i rebooted the computer but it only gets as far as asking to sign on as a live user. I try but it keeps coming back to this screen. I did a snap of the computer before i did the updates but caanot find a way to this. All i get is a chance to log off in top right hand corner.
I have a Samsung N150 Plus
Thanks for any help you can give a complete novice