Hi,
Here is what helped me:
I have a MacBook pro 2011 running windows 8.1. After installing windows, my screen brightness was all the way up and hurting my eyes, and would not change, no matter what I did. I did not install any devices, and happened upon this fix by accident.
1. go to your desktop screen and right click. On the options menu that comes up check Screen Resolution.
2. on the Screen Resolutions Page click on Advanced Settings.
3. the Generic PnP and NVIDIA GeForce 320M screen should pop up. When it does, click on the Properties button.
4. The new pop up window will say 'NVIDIA GeForce 320M Properties. Now click on the Driver tab.
5. After clicking on Driver, you will see buttons along the left side. Click on the last button. It will say Uninstall. {To uninstall the driver - Advanced}.
I let the computer uninstall the software. My screen flickered on and off 2 times, and when it came up, the screen was darker. I then checked my brightness settings by moving the brightness up and down, and it worked!!! I honestly hope this works for you, too!