Apple Support notes that after installing the Boot Camp Support Software on a MacBook Air (Mid 2012), Microsoft Windows 8 may not start, or may start with a low screen resolution (VGA).
Press and hold the power button until your Mac turns off.
Press the power button to turn it back on.
When you hear the startup chime, hold down the Option key until your disk volumes appear in Startup Manager.
Double-click your OS X volume (named Macintosh HD by default).
After OS X starts, from the Apple () menu, choose Software Update.
The Mac App store should appear with a list of available updates. Download and install the MacBook Air EFI Firmware Update 2.6 or later, or manually install it from Apple Support Downloads.
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