Probably no reason to reinstall, just boot
into "recovery mode" . You will come to a menu :
> > Please choose 'Drop to root shell prompt'
........ type passwd <Enter>
When the 'root password' is set, then :
type adduser <user name> <Enter>
( user name is the name for your new 'user account'
which is required to login to a 'Desktop' as a 'non
root user' )
You will be asked for another password, so you will
have two to remember !
Next you can either restart with <Ctrl-Alt-Delete> or
do the command : su - <username> and next : startx
to go to your Desktop.