hi
read the answer given in the below link
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if that does not resolve the issue:
This article discusses how to troubleshoot issues when you are installing a service pack for Windows Vista or for Windows Server 2008.
http://support.microsoft.com/kb/947366
Use this forum at the below link for all issues related to Windows Vista SP1, Windows Vista SP2, and Windows Server 2008 SP2.
http://social.technet.microsoft.com/Forums/en/itprovistasp/threads
or repost in the windows update forum at the below link
http://answers.microsoft.com/en-us/windows/forum/windows_vista-windows_update?page=1&tab=all