Reminder: To run Windows XP/Vista/7 on Hyper-V, you need to use Generation 1 virtual machines

I'm using Windows 8.1's Hyper-V virtual machine platform for many things, for instance for testing during software development and my writing. Sometimes, I need to get back to an older operating system version in a virtual machine, and today, I needed to install a Windows Vista virtual machine.

I was happily creation a new virtual machine for this operating system, and was using the newest generation 2 for my virtual machine, as I'm using for most of my virtual machines running Windows 8 or Windows Server 2012 R2.

I should have remembered that Gen 2 virtual machines only work from Windows 8 and Server 2012 onwards, and are not supported with older operating system version. So, what happens if you try to install Windows Vista or Windows 7 on a Gen 2 virtual machine in Hyper-V? It simply won't boot!

Here's what Hyper-V console (the Virtual Machine Connection window) says in this case:

Error: Hyper-V
Boot Failed. EFI SCSI Device.
No Operating System was loaded. Press a key to retry the boot sequence...

To fix this situation, you need to re-create your virtual machine's configuration file. First, delete your existing virtual machine, and create it again, but this time specifying Generation 1 under the "Specify Generation" step of the wizard.

Today's takeaway: In Hyper-V Generation 2 virtual machines, the operating system must be at least Windows Server 2012 or Windows 8, and a 64-bit version.