You can install an OEM copy of Windows 7 on a PC

Under Microsoft's arcane licensing rules, you can legitimately purchase buy microsoft office 2016 copies of Windows 7 (any edition). However, the license agreement with those copies explicitly prohibits you from using that software on a PC you build or refurbish for your own personal use. Crazy, huh?

You can find OEM System Builder software from dozens of online merchants. The current price for OEM Windows 7 Professional at Newegg, for example, is $140. When I checked a few minutes ago, Amazon was offering microsoft windows 7 professional packages from multiple sellers at prices ranging from $101 to $150. When I checked just now, a package specifically intended for refurbished PCs cost only $50 for a 64-bit copy.

There are no technical limitations to prevent you from using microsoft windows 10 home software on your own PC, although this software will work only for a clean installation and not for an upgrade. In the past, Microsoft has been remarkably inconsistent in its advice to customers about whether this practice is allowed. (See "Is it OK to use OEM Windows on your own PC? Don't ask Microsoft.")

To make the subject even more confusing, Microsoft briefly changed its licensing rules with Windows 8, adding a Personal Use Rights clause that allowed individuals to buy OEM Windows and install it on personal PCs. That change lasted exactly one year: with the launch of Windows 8.1, Microsoft restored the old licensing terms.