I'm just curious as to the mechanics Microsoft Update, and or Vista uses to determine when new updates become available. This morning, I installed Microsoft Office 2003 on an otherwise up to date installation of Windows Vista Enterprise. Immediately after the installation of office was complete, I checked for updates, no updates available. I rebooted the machine, checked for updates and still, no updates available. I then left the machine on and walked away for an hour or so. When I came back, I checked for updates again, and got all the relevant office updates. Is there some sort of background indexing of installed software that has to take place before the system becomes aware of new programs which need updating?