Vista SP1 stand-alone packages do not contain updated SP1 Help Files

Windows Vista SP1 stand-alone packages do not contain the updated Windows Vista SP1 Help files. The updated Help files have been excluded from the stand-alone SP1 packages to reduce the size of the packages. However, the updated Windows Vista Help files are contained in the retail and OEM versions of Windows Vista that include SP1. Therefore, if you perform a clean installation of a version of Windows Vista that includes SP1, you do not have to add an updated Help file.

The updated Windows Vista Help file packages are named "Update for Help Files." These files are packaged separately for each language.

You must manually install the "Update for Help Files" package to obtain the updated Windows Vista Help files in the following scenarios:

•You install Windows Vista SP1 on a computer that is running the release version of Windows Vista by using Windows Update or by using a Microsoft Update Standalone (MSU) package for Windows Vista.

•You have a Windows Vista Enterprise SKU installed or a Windows Vista Ultimate SKU installed, and then you install a new language by using the language packages.
In this scenario, you must manually install the updated Help file because the "Update for Help Files" package uses the language that corresponds to the content language. Packages of "Update for Help Files" are language specific. For example, you cannot install the German version of the "Update for Help Files" package on a Windows Vista-based computer unless that computer already has the German language installed.

•You remove a language package from a Windows Vista-based computer after you install the "Update for Help Files" package for that language pack that you removed.
In this scenario, the "Update for Help Files" packages are automatically removed.

You can download the MSU package for the "Update for Help Files" package through the Microsoft Download Center. To do this, visit the following Microsoft Web site:

http://www.microsoft.com/downloads/details.aspx?FamilyID=dd4affa2-f435-4c42-82da-110948c001c1 

Update for Windows Vista for x64-based Systems (KB937286)

For more details : Check this KB article

(Thanks: Bink.nu)