Vista SP2 now available in Windows Update
Looks like Vista SP2 is now available in Windows/Microsoft Updates.
http://technet.microsoft.com/en-us/windows/dd262148.aspx
Download types
Windows Update . Windows Update contains SP2, so SP2 will be installed automatically on computers that are set to receive automatic updates. However, before SP2 is installed, the user must accept the Microsoft Software License Terms.
Stand-alone package . You can download SP2 from the Microsoft Download Center at http://go.microsoft.com/fwlink/?LinkId=145430.
Integrated installation. SP2 is integrated into the Windows Server 2008 SP2 installation DVD, and it is also available as part of the media kit for Volume License customers as well as TechNet and MSDN subscribers. Deployment Guide
http://technet.microsoft.com/en-us/library/dd351467.aspx