http://www.zdnet.com/article/you-have-o ... dows-7-pc/
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Downgrade rights Any new PC you buy that has Windows 10 Pro preinstalled by the manufacturer comes with downgrade rights to Windows 8.1 Pro or Windows 7 Professional, for as long as Microsoft provides support for those earlier versions. You must supply your own installation media, and you have to activate manually.
Of course, there are perils and pitfalls associated with running the increasingly aging Windows 7, especially on newer hardware. System manufacturers have no economic incentive to develop drivers and support tools for older Windows versions. Most downgrades will work, but some components might not work properly, or at all.
On new systems with Intel's Kaby Lake processors, versions of Windows before Windows 10 will not be supported at all. That doesn't prohibit you from trying to install Windows 7 on one of these new devices, but don't expect any support from the PC maker or from Microsoft when you inevitably run into problems.