by boco » 01.04.2017, 22:39
Without verification, it does not notice the file is corrupt, and so it doesn't rollback and deletes the good copy. It also needs to be said that the good copy might be outdated, so, while it will rollback successfully, you do not get the new patches, anyway.
Microsoft update catalog: http://catalog.update.microsoft.com/v7/site/
Windows Install media download: https://support.microsoft.com/en-us/help/15088/windows-create-installation-media