The same thing happened in an equally mysterious way to me....Just remove the primary controller, reboot, you'll probably go into safe mode.  Check the performance tab to monitor 32bit support.  Reboot, hopefully into windows and let new hardware be installed.  If all is not well, go through the add new hardware wizard and let the drivers be installed from C\Windows\System.  You may have to repeat this more than once.   If you cannot turn off the computer easily after removing the controller, hold the reset button about 10 seconds and it should turn off.  Then wait a minute to reboot.   Hope this works.  It did for me and everything is A-okay.

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