Refer: http://bootables.net/windows-10-updates-stuck-download/
Open a command terminal as an administrator and shutdown two services:
- C:>net stop wuauserv
- C:>net stop bits
Go to the following folder and delete everything, a few folders may stick.
- C:\Windows\SoftwareDistribution
Reboot your computer and update services should be already restarted, you can restart them manually like this with another admin terminal.
- C:>net start wuauserv
- C:>net start bits