Availability reports in MOM 2005

http://blogs.technet.com/operationsmgr/archive/2009/07/22/the-monthly-availability-report-in-mras-may-be-missing-some-dcs-and-exchange-servers.aspx

Step by Step for using Certificates to communicate between agents and the OpsMgr 2007 server  

http://blogs.technet.com/operationsmgr/archive/2009/09/10/step-by-step-for-using-certificates-to-communicate-between-agents-and-the-opsmgr-2007-server.aspx