The reason your PC was force restarted while you were in the middle of doing something is because Windows 8.1 is designed that way, to annoy you.  Windows 8.1 has a lot of annoying features but is better than Windows 8 which was even more annoying.  If you don’t want forced restarts, you can disable updates.  I believe updates is what’s causing the forced restarts.  I just don’t understand why Windows 8.1 won’t wait to do it’s update thing until I shutdown.  Microsoft want’s you to use Windows 8.1 as much as possible.  I am not a fan of Windows 8 or 8.1  I dual boot Elementary Luna OS which resembles Apple OSX and is linux based.  I use Windows 8.1 only when necessary. windows 8.1 forced shutdown