Windows 10 Insider Preview 17666.1000 - failed install attempt - 0xc1900101

It's an old solution, helped me a lot of times.

- Create a bat file.

- Edit with notepad or something else.

- Paste this:

@ECHO OFF
echo Simple Script to Reset / Clear Windows Update
echo.
PAUSE
echo.
attrib -h -r -s %windir%\system32\catroot2
attrib -h -r -s %windir%\system32\catroot2\*.*
net stop wuauserv
net stop CryptSvc
net stop BITS
ren %windir%\system32\catroot2 catroot2.old
ren %windir%\SoftwareDistribution SoftwareDistribution.old
ren "%ALLUSERSPROFILE%\application data\Microsoft\Network\downloader" downloader.old
net Start BITS
net start CryptSvc
net start wuauserv
echo.
echo Task completed successfully...
echo.
PAUSE

- Save

- Run as administrator.

As you can see from the code, it just stops WU services, renames related directories and runs the services again.

Hope it will help.