Mastering Windows Server 2016 Hyper-V

There is a difference between what is supported and what will work. Microsoft
supports only operating systems on Hyper-V that are themselves supported by the
vendor. For example, Microsoft no longer supports Windows Server 2003, which
means that Hyper-V can no longer support it as a guest operating system, but it will
run a virtual machine. In a production environment, you typically should be running
only operating systems supported by the vendor to ensure that patches are received
and that in the event of a problem, you can get help from the vendor. If you have a
Windows Server 2003 application, however, it most likely would run on Hyper-V just
fine.