Switch on/off Nvidia card on Dell Vostro 3700/3500

This URL provides the details to switch on/off the Nvidia card on a Dell Vostro 3700 or 3500 laptop:

https://bbs.archlinux.org/viewtopic.php?pid=882737#p882737

When the nvidia card is switched on, it uses the nouveau drivers, and some stability issues have been found.