VHD (file format) - Wikipedia
https://en.wikipedia.org/wiki/VHD_(file_format)
VHD (Virtual Hard Disk) and its successor VHDx are file formats representing a virtual hard disk drive (HDD). They may contain what is found on a physical HDD, such as disk partitions and a file system, which in turn can contain files and folders.
7 Ways To Open Virtual Hard Disk Images For Read And Write Access
https://www.raymond.cc/blog/access-virtual-hard-disks-easily-in-windows-7/
Virtual disk formats are sometimes interchangeable between products. The mounted virtual VHD will now be listed as a standard hard drive in Explorer with read and write access.
VHD File Extension - What is a .vhd file and how do I open it?
https://fileinfo.com/extension/vhd
A VHD file contains a virtual hard disk image used by Microsoft Windows Virtual PC, a Windows virtualization VHD files may be used to install multiple operating systems on a single computer, test...