Question: Is it permissible to buy OEM software online?

Answer: OEM (=original equipment manufacturer) software is licensed to computer manufacturers and stores to install on computers they sell, not for direct sale to end-users. The license is granted to a "system builder," defined in Microsoft's OEM license as: "an original equipment manufacturer, an assembler, a refurbisher, or a software preinstaller that sells the Customer System(s) to a third party."

Generally, OEM software may not be resold, except for unopened copies to another "system builder." Thus, selling OEM software to an end-user without accompanying hardware, or selling used OEM secondhand, is a breach of the license. Furthermore, sites offering "OEM versions" at great discounts (e.g., Adobe Photoshop) are often counterfeit copies.

OEM licenses are usually granted to the specific hardware (usually motherboard) to which the OEM software was initially installed ("Licensed Device"). Thus, according to the licensing terms (which must be accepted also by the end-user), when a person buys a new computer, he may not transfer his OEM software to the new machine.

For more information, see: Microsoft OEM licensing FAQ, Microsoft OEM System Builder license, and OEM section of Microsoft Software License Agreement.