A software update is available for versions of Windows Vista that include the Windows BitLocker Drive Encryption feature

This article describes software update 935509. This update is available for versions of Windows Vista that are mentioned in the "Applies to" section and that include the Windows BitLocker Drive Encryption feature.

Note This software update is a prerequisite for Windows Vista Service Pack 1 (SP1). This update helps improve reliability when you install or remove Windows Vista SP1.

Two or three updates are required before you install Windows Vista Service Pack 1. The updates that are required depend on the edition of Windows Vista that you are upgrading. Prerequisite update 935509 is only applicable to Windows Vista Enterprise and to Windows Vista Ultimate. The other prerequisite updates that are discussed in this article apply to all editions of Windows Vista.

Before Windows Vista SP1 is released, these prerequisite updates will be delivered to most users through Windows Update as part of regularly scheduled monthly updates. These updates will be installed together with other updates that will require that you restart the computer. An additional restart will not be required. Therefore, this delivery method will simplify installation of these prerequisite updates.

Customers who decide to install Windows Vista SP1 by using the stand-alone installer, instead of by using Windows Update, will not have to install the prerequisite packages separately. The prerequisite packages will be installed by the stand-alone installer if they are necessary.

The following three updates are required before you install Windows Vista SP1. However, these updates are also recommended if you do not intend to install Windows Vista SP1. These updates help improve reliability and performance when you install future individual updates from Microsoft.

• Update 935509 contains an update that you must have to correctly service Windows BitLocker Drive Encryption-capable computers. This update is applicable to only the following editions of Windows Vista that include Windows BitLocker Drive Encryption:
  • Windows Vista Enterprise
  • Windows Vista Ultimate
  This update is necessary to install and to uninstall Windows Vista SP1 successfully on these editions.
• Update 938371 updates several internal components that Windows Vista requires in order to install or to uninstall Service Pack 1 more reliably. This update must be applied separately before you install Windows Vista SP1 to make sure that Windows Vista SP1 can be installed or removed from the computer. This update is necessary to install and to uninstall Windows Vista SP1 on all editions of Windows Vista. This update will be available on the Windows Update Web site soon after the release of update 935509 and before the release of Vista SP1.
• Update 937287 is a prerequisite package that contains updates to the Windows Vista installation software. The installation software is the component that handles the installation and removal of software updates, language packs, optional Windows features, and service packs. This update is necessary to successfully install and uninstall Windows Vista SP1 on all editions of Windows Vista. This update will be available on the Windows Update Web site soon after the release of update 935509 and before the release of Windows Vista SP1.

Update information

Software update 935509 is available from the Windows Update Web site. To obtain this software update, follow these steps:

1. Click Start
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   , click Control Panel, and then click Security.
2. Under Windows Update, click Check for updates.

Prerequisites

There are no prerequisites for installing this update.

Restart requirement

You must restart the computer after you apply this update.

Update replacement information

This update does not replace a previously released update.

Update removal information

You cannot remove this update.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: