A great article on Windows Vista Kernel (Part I, II and III)
The scope of this article comprises changes to the Windows Vista™ kernel only, specifically Ntoskrnl.exe and its closely associated components. Please remember that there are many other significant changes in Windows Vista that fall outside the kernel proper and therefore won't be covered. This includes improvements to the shell (such as integrated desktop search), networking (like the new IPv6 stack and two-way firewall), and the next-generation graphics model (such as Aero™ Glass, Windows® Presentation Foundation, the Desktop Window Manager, and the new graphics driver model). Also not covered are the new Windows User-Mode and Kernel-Mode Driver Frameworks (UMDF and KMDF) since these are back-level installable on earlier versions of Windows.