Microsoft System Center Operations Manager 2007 has recently released CU3 (Update 3)
the install proceedure varies depending on what version you have installed.
how can you tell what version you have?
Open the SCOM Console.
Under ‘Monitoring’ select the item ‘Discovered Inventory’
Change the Scope of the items displayed to ‘Heath Service’ (there is a scope button on the tool bar on top)