While upgrading to Windows 10, if you ever got the famous 80240016 Windows update error message saying that “Windows 10 couldn’t be installed” (as the screnshot below shows), don’t worry at all as it needs a small fix:
All you need to do is to open Windows Defender by searching for it in Control Panel (on Windows 7) or in the start screen (on Windows 8/8.1) -> open the Settings tab -> uncheck “Turn on real-time protection (recommended)”
The rest is a piece of cake then. Just re-try the upgrade process and you will see it will never fail on you again:
If you still had issues upgrading to Windows 10, please let me know in the comments section and I will try my best to help you.