Use SFC (and DISM on Win 8) to remove any incomplete updates, then the System Update Readiness tool again. See the following for bothe Windows 7 and 8 techniques:
Error 0x800B0100 when you try to install Windows Updates or Microsoft Updates and Windows Update error 0x80070490 (yes, it is a different error number, but the fixes apply to both issues, specifically using SFC and DISM for Win 8, which back out some of the updates that had been partially installed).
It may then require going through the normal Windows Update process multiple times but should resolve the issue.
Please let me know if that fixes the issue.
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