There are two available schema extensions for Vista.  One is to enable a central recovery solution for BitLocker and the other is for configuration of network authentication.  Details below. 

 

Configuring Active Directory to Back up Windows BitLocker Drive Encryption and Trusted Platform Module Recovery Information

Source: http://www.microsoft.com/downloads/details.aspx?FamilyID=3a207915-dfc3-4579-90cd-86ac666f61d4&DisplayLang=en

 

Active Directory Schema Extensions for Windows Vista Wireless and Wired Group Policy Enhancements

Wireless and wired clients running Microsoft® Windows Vista™ support enhancements that can be configured through Group Policy settings and are supported by domain controllers running Windows Server® Code Name "Longhorn" (now in beta testing). To support these enhancements for an Active Directory® directory service environment consisting of domain controllers running Windows Server 2003 or Windows Server 2003 R2, the Active Directory schema must be extended. This article describes how to extend the Active Directory schema to support these new features for Windows Vista wireless and wired clients.

Source: Active Directory Schema Extensions for Windows Vista Wireless and Wired Group Policy Enhancements