Support for Windows Vista Service Pack 1 (SP1) ends on July 12, 2011. To continue receiving security updates for Windows, make sure you're running Windows Vista with Service Pack 2 (SP2). For more information, refer to this Microsoft web page: Support is ending for some versions of Windows.
Microsoft has released security bulletin MS08-029. The security bulletin contains all the relevant information about the corresponding security update. This includes file manifest information and deployment options. To view the complete security bulletin, visit one of the following Microsoft Web sites:
Microsoft Antigen 9.0 for Exchange, Microsoft Antigen for Exchange Service Pack 1, Microsoft Antigen for SMTP Gateways, Microsoft Antigen for SMTP Gateways Service Pack 1, Windows Defender, Microsoft Forefront Client Security, Microsoft Forefront Security for Exchange Server, Microsoft Forefront Security for SharePoint