mitchellh/vagrant — pull request #4208 by mwrock (2014-07-17 09:57:11+00:00)
Title: accept vhd as well as vhdx file types on hyper-v

This allows both .vhd and .vhdx as supportable file extensions for hyper-v. Although vhdx is the more modern and possibly preferred extension. Microsoft still ships evaluation windows VHDs in using the older .vhd format. So supporting this format means vagrant boxes can be made from these VHDs without having to migrate them.