Event log automatic backup
You'll see this event logged if you have your event log properties set to 'Archive the log when full, do not overwrite events' and its showing you where the archived log is stored. This can be set in the Windows Event Viewer by right clicking on a log and selecting 'Properties'. Once in properties, choose the 'Archive the log when full, do not overwrite events' radio button and hit apply. This is on a log by log basis, so you'd have to set it for each log.