A new system readiness tool is available from Microsoft:

This article describes the System Update Readiness Tool for Windows Vista, Windows Server 2008, Windows Server 2008 R2, and Windows 7.
You may become unable to install updates from Windows Update, due to inconsistencies in file data or registry data. By installing the System Update Readiness Tool, you can resolve these inconsistencies and you will be able to install updates from Windows Update. After the System Update Readiness Tool is installed, install updates again from Windows Update.
Reference and download:

Description of the System Update Readiness Tool for Windows Vista, for Windows Server 2008, for Windows 7, and for Windows Server 2008 R2