Hi all...
if anyone is interested ... here is how i did for switching off the Discrete Card (NVIDIA) in my case
1)download the ACPI_CALL module with this command:
git clone http://github.com/peberlein/acpi_call.git
(you need to have the git utility and his dependencies--> install it via software manager)
2) cd acpi_call
3)make
4)insmod acpi_call.ko
5) ./asus1215n.sh off
point 3) 4) 5) you have to become root
bye
Marzio