14 DAY TRIAL // If the brightness controls on your MacBook Pro no longer respond after updating to Windows 8.1 in Boot Camp, don’t despair, there’s an easy fix for that.
Apple has released a Support document containing a guide for restoring the functionality of your F1 and F2 keys as the brightness controls on your MacBook Pro.
The company explains: “After upgrading from Windows 8 to Windows 8.1 on a MacBook Pro (17-inch, Early 2011 or Late 2011), the F1 and F2 keys may no longer control the brightness of the computer's built-in display.”
To fix the problem, customers need to perform a Repair Install of the Boot Camp 5.1 drivers. Users will need a USB flash drive that contains the proper Boot Camp 5.1 drivers and then follow some steps to perform the Repair Install. The full guide is available on Apple’s KB article TS5382.