I have a late 2011 15" MBP running Windows 8 with Boot Camp 5. Everything is up to date (I tried using the default Boot Camp drivers as well as the latest AMD Catalyst Mobility drivers--same behavior). The graphics card is the Radeon HD6770M. The problem is that the screen is at maximum brightness, and nothing will change that. The brightness keys act as though they might work (the meter bars move); the adaptive brightness is turned off. Manually changing the brightness in the Windows Charms has no effect; neither does the Windows Display settings. Any ideas?