daniele@zorin:~$ sudo /usr/lib/nvidia-173/bin/nvidia-xconfig

Using X configuration file: "/etc/X11/xorg.conf".

VALIDATION ERROR: Data incomplete in file /etc/X11/xorg.conf.
                  Device section "Default Device" must have a Driver line.

Backed up file '/etc/X11/xorg.conf' as '/etc/X11/xorg.conf.backup'
New X configuration file written to '/etc/X11/xorg.conf'