Clear All Windows 2008 R2 event logs

If you want to clear the event logs in a Windows Server system, you can fire up Event Viewer, browse to the desired log and from the Actions menu select Clear Log.... But if you want to clear all the System and Application logs at once, you'd better use the `wevtutil' command line utility Microsoft offers. A Windows PowerShell command like this will do the job: 

wevtutil el | foreach { wevtutil cl $_ }

(from http://skalkoto.blogspot.com/2011/08/clear-all-windows-2008-r2-event-logs.html)