Original equipment manufacturer, or OEM, software is not legal when used in violation of its associated software license. OEM software is bundled and sold with hardware. The end-user license agreement, or EULA, usually states the software must be used in conjunction with the hardware; not doing so violates the license.
Hardware manufacturers purchase OEM software in large quantities for inclusion in their product. This type of software is often an older version or contains limited features, sometimes labeled as special or limited edition. While not common, legal versions of OEM software that are sold separately do exist and are distributed by the publisher or its authorized agent.