If you are continuously getting Windows Update Fails issue then it is the time to reset Windows Update Components to its default value.
This tool was primarily designed to solve issues related to Windows Update Components.
Reset Windows Update Components
Before starting, remember to make a backup the registry.
Then select the option "Reset Windows Update Components". This option will stop Windows Update services, while cleaning the components and restore the initial settings.
You will see that it started to reset Windows Update Components automatically. In a few minutes the process will be completed.
After that, Install the latest Windows Update Agent: https://support.microsoft.com/en-us/kb/949104.
Finally, restart your PC to save the changes.
The Windows Update service could not be stopped
If Windows Update Service won't stop then run this tool on safe mode.
Most of the ways you access Safe Mode involve getting into the Windows recovery environment first.
The easiest way to get to the recovery environment is to hold down the Shift key while clicking Restart.
If the error persists, your Windows installation can be found in poor condition and requires repair or reinstall.