Another new OS. Except this one is completely free (as in, you can use it legally without paying for it which must be a first from Microsoft!). However… besides being sufficiently cut-down to run just Hyper-V, you also only get a command line. So it has the same user-friendliness as Server Core, without most of the functionality. It’s probably not ideal for a production environment (after all, most of Windows server is missing and there’s no support) but is great for testing- I’ve got it running as the secondary boot on a 3-year old Dell laptop and it does exactly what it says on the tin- I can create an entire Hyper-V environment on it from my W8 workstation, including being able to use all the new PowerShell commands.