After you uninstall some software updates in Windows Vista or in Windows Server 2008, some assembly files may still reflect the updated version instead of the original version of the files
On a computer that runs Windows Vista or Windows Server 2008, you uninstall some software updates. However, after the operation finishes, some of the software assembly files may reflect the updated version instead of the original version of the files.
For example, on a Windows Vista-based computer, assume that you have the 2007 Microsoft Office system installed. If you install and then uninstall 2007 Office system Service Pack 2 (SP2), some assembly files in the global assembly cache (%SystemRoot%\Assembly\GAC) remain from the 2007 Office system SP2 version.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB967756.