I've got 2 E6420's sitting here on my desk, both of them have the Optimus with Nvidia 4200m. I've got windows 8 running on both machines. After jumping through all the hoops to get my brightness settings to work properly while in single screen mode(had to use the oldest intel driver on dells site for windows 7).
Now when I plug in my secondary screen my brightness goes to MAXIMUM and will NOT adjust. The reason for this is because when you plug your HDMI in then it uses the Nvidia graphics card. I have used every driver on dell's website for windows 7 and 8 and I have also used the latest driver from Nvidia's website. No change. I have attempted to disable the Nvidia in my device manager, but then I get no response on my secondary screen. I have attempted to turn off optimus in the bios and that just resulted in me re-formatting windows 8.
So here is my question, why in the *** doesn't Dell have drivers that will actually work for their machines? I've got 5 of these E6420's and luckily my other 3 don't have the Nvidia.