Windows 7 VHD

The most exciting feature for me in Windows 7 is the ability to boot to a Virtual Hard Disk (VHD). Booting from VHDs means booting the machine as if running from primary hard disk so your operating system will leverage all the hardware available in your system like Graphics, Wireless, USB etc.
How to Create a Windows 7 VHD at Boot to Start with from Boot

http://www.sevenforums.com/tutorials/2953-virtual-hard-drive-vhd-file-create-start-boot.html