Description of the Windows Vista and Windows Server 2008 installation software feature update released April 28, 2009
This article describes the software update that applies to versions of Windows Vista and Windows Server 2008 that are mentioned in the “Applies to” section. When Windows Vista Service Pack 2 and Windows Server 2008 Service Pack 2 are released this software update will be a prerequisite to install the service packs. Additionally, this update improves reliability when you install or remove Windows Vista and Windows Server 2008 SP2.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB955430.