Here are the instructions to get started with a virtual hard disk on Windows 10.
On Windows 10, a virtual hard disk (VHDX or VHD) is a file that can use a ".vhdx" or ".vhd" extension and acts like a physical hard drive, but with the difference that this is a file stored on a real disk.
Using either format (.vhdx or .vhd) for a virtual drive, you can store any files, including documents, pictures, videos, boot files, and an entire OS installation. The only differences between the two formats are that a .vhdx file supports a maximum size of 64TB, features resiliency against power failure, and provides better performance.
Typically, a VHD comes in handy to add extra storage to a Hyper-V virtual machine, and thanks to its ability to support other OS installations, you can even use this storage virtualization technology to create a dual-boot system without modifying an existing partition.
Full story from the WindowsCentral blog...