How Vista does it's notification
Microsoft Update Product Team Blog : Office 2007 SP1 Update Availability:
http://blogs.technet.com/mu/archive/2007/12/13/office-2007-sp1-update-availability.aspx
On Vista, if you have notify me that patches are available, you will see that the icon will tell you that patches are available.
Then when you launch the WU/MU interface you will see that patches are offered up.
Then when you click on the details, you will see that Office 2007 sp1 is offered.
By that process, if you are not awake and brain dead, you might end up with Office 2007 sp1 on your system. I've done tests here and if Auto updates is turned on a NON SP1 (beta test) Vista system, or if download but notify is enabled, neither option will install Office 2007 sp1 on a system.
So bottom line, I only saw Office 2007 sp1 auto installed when I was running Vista sp1 beta or was pointed to a beta-MU site. And the setting "Check for updates but let me choose whether to download to install them" is the most confusing setting and is apt to get you in trouble.
Read the complete post at http://msmvps.com/blogs/bradley/archive/2007/12/12/how-vista-does-it-s-notification.aspx