If you are like me and open lots of saved event log files (*.evtx), such as those captured by the “mdmdiagnosticstool.exe -area Autopilot -cab c:\autopilot.cab” command, you probably end up with an Event Viewer window that looks something like this:

Always opening, never closing (which you can do by right-clicking and choosing “Delete”).  Fortunately, there’s a KB article that tells you how to clean this up:

https://support.microsoft.com/en-us/help/2489761/how-to-delete-saved-logs-from-the-event-viewer

Simple process:

• Close all Event Viewer processes.
• Delete all the files from “C:\ProgramData\Microsoft\Event Viewer\ExternalLogs”.

• Start up Event Viewer and see they are gone.

Yes, this is a self-serving post to save me the trouble of finding this the next time I need to do this 🙂