<img attachment="updates_dont_install.png" align="right" caption="Updates won't install"><img attachment="windows_defender_not_running.png" align="right-column" caption="Windows Defender not running">For quite some time now (months?), my Windows 10 installation has had a problem/corruption in its Update Database that prevented it from applying some updates. At first, it was just a <i>definition</i> update for Windows Defender, which is bad enough. However, a recent update to Windows Defender <i>itself</i> could not be applied and this conflict prevented Windows from even <i>starting</i> Windows Defender Antivirus. That's not great. <clear><h>Finally: A Solution</h> Digging around online in this problem area is complicated by the fact that there are so many Windows users and so many versions and <i>so many configurations</i>. Many users offer advice when they don't know what they're talking about. A lot of threads quickly devolve into <iq>I re-installed Windows and the problem went away</iq>. Well, duh. If the muffler falls off of your car, <i>technically</i> you can solve that problem by buying a new car. I'm just not interesting in the nuclear option; it costs so much time and effort. At Encodo, we have a base image, but it still takes time to get everything back to where it was. After keying in the KB ID (Knowledge Base ID) of the update and searching a few threads, I finally landed on <a href="https://answers.microsoft.com/en-us/windows/forum/windows_10-update/windows-defender-update-kb4052623-has-been-failing/3555d9b1-006f-4dc7-b445-3368aa4daf06">Windows Defender update KB4052623 has been failing to install with error 0x80070643 for months</a>, which is an accurate description of my issue. That was encouraging. Lower on the page is a comment that recommends using the <a href="https://support.microsoft.com/en-us/help/10164/fix-windows-update-errors">Windows Update Troubleshooter</a>, a tool I'd never heard of before. It does what it advertises, at least for me.<fn> That the feedback contained two errors, one of which the tool couldn't repair wasn't encouraging, but after a restart, Windows Update was up-to-date and Windows Defender was running again. <img attachment="windows_update_troubleshooter_running.png" align="left" caption="Windows Update Troubleshooter Running"><img attachment="windows_update_troubleshooter_feedback.png" align="left" caption="Windows Update Troubleshooter Feedback"><img attachment="windows_up_to_date.png" align="left" caption="Windows is up-to-date again!"> <hr> <ft>The poor soul who wrote <a href="https://answers.microsoft.com/en-us/windows/forum/windows_10-security/kb4052623-version-4161765618052-error-0x80070643/a1e767bb-7225-4e11-998c-3a620c980f62">KB4052623 (Version 4.16.17656.18052) - Error 0x80070643 Defender Troubleshooter - gives conflicting reports</a> had another experience, but that might have been with an earlier version of the tool.</ft>