https://support.microsoft.com/en-us/kb/971058

Download and run the Windows Update Troubleshooter for Windows 8.1, Windows 8, and Windows 7.

这个工具下载之后,是WindowsUpdateDiagnostic.diagcab;尝试运行,但是没啥卵用

Manually reset Windows Update components

按照这个指示的步骤,逐个处理,第6步,注册dll,应该可以忽略的

最后,再安装最新的客户端

How to update the Windows Update Agent to the latest version

https://support.microsoft.com/en-us/kb/949104