YES, FEDORA 19.
I saw a lot of information about how to do it but doesn't work with this version. All the tutorials explain the method for older versions of Fedora, i didn't found anything about doing it on the v19 or the v18.
The GRUB menu is different (and i installed the GRUB's version from fedora installation, I only have this system ). I can enter to the recovery console but asks me the root password, so this doesn't solves anything.
If anyone knows a way to do it; or if it's impossible, please tell me why.
rw init=/bin/bash
in the command line. That way you boot directly to a shell, where you can do passwd. If this does not work, boot from a live cd (of any distro), mount the system, chroot into it and passwd there. If any of this works, let me know and I'll write a proper answer. If not, be more specific about why it fails.