On updating my clean install of Windows 10 to version 1079 via Windows Update, it hangs / freezes at 80%. I spent a lot of time looking for the fix for this online, but in the end I fixed it by waiting for AGES (many hours) for it to finish. It actually started working while I was looking for ways to fix the hang.
I also tried using the Windows Update Troubleshooter, which seemed to have no effect, but may have somehow helped my situation.