The nVidia driver actually greyed out and prevents you from selecting the nVidia GPU for apps in it's known-list. Firefox and Chrome are on the list of programs that can only use the Intel GPU. You can always copy Firefox.exe to Firefox2.exe and then it's not on the known-list. You can browse to it from the nVidia control panel thing, then set that to use the nVidia GPU. Unfortunately, it tends to crash the whole OS a lot if you do that, which seems pretty ridiculous. I tried both Firefox and Chrome and eventually gave up and left them on the Intel GPU.