With Windows 8 that all changes and Microsoft has decided to actively support individuals who want to build their own machines or run Windows 8 as a virtual machine. That support comes in the form of a new license option called the Personal Use License for System Builder (PULSB).
With PULSB, Microsoft is dumping the full retail license used in previous versions. Instead it is offering a version of Windows 8 to be installed as the main operating system on a single system meant for personal use, or in a virtual machine running on an existing PC (running any legal OS such as Windows 7, Mac OS X, or your favorite flavor of Linux)."
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