The Virtual Hard Disk (VHD) is the container for the installed operating system. Boot from VHD is a new technique for installing and maintaining operating system environments. Unlike virtual machines, the operating system that is running from a “boot from VHD” environment is using the actual hardware instead of emulated hardware. One thing that is not well known is how easy it is to create the initial .VHD file and install the operating system into it. The key is The Windows Preinstallation Environment (WinPE) and Windows Automated Installation Kit (WAIK). The following video below shows a Windows 7 (download)and Windows Server 2008 R2 (download) Dual Boot via VHD.
Source:→ Keith Comb