1) “Critical Update for Windows Small Business Server 2003: Vista and Outlook 2007 compatibility (KB 926505)”. This is a ‘critical’ (high priority) class update targeted at all SBS servers with SBS SP1. That means Automatic Updates will install this. For more information see http://support.microsoft.com/kb/926505 and the following post on this Blog: http://blogs.technet.com/sbs/archive/2007/02/09/sbs-vista-client-update-ripcurl-now-available.aspx
This is the same package that has been available for download in the download center since February, just moving to a push distribution from a pull to proactively ensure that the platform is ready to accept Windows Vista with no other issues. You still need to read this KB and install the other required updates to get the full SBS experience with Windows Vista.
2) “Update for Windows Small Business Server 2003 (KB936594)” – otherwise known as the Windows Server SP2 RSS fix. The RSS fix is an “Update” (optional) class update targeted as all SBS servers with SBS SP1 and Windows Server SP2 to disable the Scalable Networking Pack in Windows SP2 that was interfering with NAT on many newer SBS servers. For more information see http://support.microsoft.com/kb/936594 and the following post on this Blog: http://blogs.technet.com/sbs/archive/2007/04/24/common-networking-issues-after-applying-windows-server-2003-sp2-on-sbs.aspx