I have reinstalled Windows 7 on my Dell Precision M4600. I installed the chipset (restarted), then video and network driver (in that order). However I am not able to dim the light using fn-up/down.
I installed the drivers first without any Windows update. Using the control point software, I got the little dialog showing the dimming. However after updating the dialog displays but it is fixed; that is, nothing happens when I try to dim the screen. The keyboard dimming works.
I am having NVIDIA 1000 Quadro M graphic card if that is any help. Turning off Optimus in BIOS fixes the problem but I have never had this problem before reinstalling.