Mark speaks about new kernel constructs in Windows 7 and the dismantling of the Dispatcher Spin Lock and redesign and implementation of its functionality into separate components. Resulting in Windows 7 being able to scale to 256 processors, along with Boot from VHD and other OS enhancements.

http://channel9.msdn.com/shows/Going+Deep/Mark-Russinovich-Inside-Windows-7/

Mark Russinovich: Inside Windows 7