In an interesting twist, Microsoft has confirmed that Windows 8 will feature the first-rate, enterprise-echelon Hyper-V machine virtualization hypervisor. This will mean that Windows 8 users will be able to run almost every other operating system inside a window, including Windows 7 and XP, SUSE and Red Hat Linux, and more (including Ubuntu) with a little hacking. Prior to Windows 8, Hyper-V was only available in Windows Server 2008 or as a standalone OS.
Now, at its most basic, this will just mean that you wont have to download the free (and excellent) VirtualBox software if you want to virtualize a guest operating system a very useful feature for power users and developers who want to try out different build and runtime environments, but not exactly a killer feature for consumers. Unless what if Hyper-V comes with a copy of Windows 8 (or 7) guest OS pre-installed?
Just imagine this for a moment: you boot up into normal, running-as-root/administrator Windows 8. Once Windows 8 finishes loading, Hyper-V then boots up a virtualized instance of Windows 8 so you have Windows 8, and another completely separate copy of Windows 8 running in a window. You can then do anything you like with the virtualized OS without affecting the main, host OS. At its most basic, you could use the in-a-window OS to safely surf lewd and/or malware-ridden websites but you could also use it to open untrusted files, play around with system files, and so on. Virtualization is, in essence, the best security sandbox money can buy.
Furthermore, bundling a virtual machine manager with Windows 8 means that Microsoft can relax its truly heroic backwards-compatibility efforts. This isnt to say that Windows 8 wont run legacy, Windows XP-era software, but if it happens to be slightly glitchy then just install XP under Hyper-V. Microsoft could also make this compatibility layer transparent: imagine opening an incompatible Windows XP program, but instead of being told it wont run, Windows 8 automatically opens a virtualized instance of Windows XP, and then the program.
Source : msdn
