Failed Logon Event 675 for user Administrator

Recently setup ADAudit plus and there are thousands of failed Administrator logins. Because we have a mix of 2003 and 2008 domain controllers my searching shows there is a difference in encryption for the two but I thought adding https://support.microsoft.com/en-us/kb/948963  to 2003 would take care of those errors, doesn't look like it. I need to clean up this white noise in case there is something serious happens. I came across this https://support2.microsoft.com/default.aspx?scid=kb%3Ben-us%3B305144 and some other support topics that might be related to my problem but I want to check with experts to see if that is really the case and what do I need to do to fix it. It is documented here as well http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1005469 but I'm confused on the Right-click DOMAIN\EXC$ and click Properties. part not sure what DOMAIN\EXC$ means

The event error
Pre-authentication failed:
       User Name:      Administrator
       User ID:            DOMAIN\administrator
       Service Name:      krbtgt/domain
       Pre-Authentication Type:      0x0
       Failure Code:      0x19
       Client Address:      10.1.1.81


For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.