Open door after Xubuntu upgrade: Disable guest account

I finally updated Xubuntu to 11.10 and changed to lightdm for the login. This add a guest account to the system which allows access to the computer and special the NTFS partitions whit no password or any other authentication. Yes, whit out encryption there is any way no real security, but we don't have to made it to easy. This helps:

Turn of the guest account in lightdm:

In the file /etc/lightdm/lightdm.conf add bellow [SeatDefaults] the line

allow-guest=false

Edit the file easy whit this line:

sudo mousepad "/etc/lightdm/lightdm.conf"

Don't forget to restart the Xserver (or the computer) after.