A factory-installed Windows 10 PC differ from previous versions of Windows. The Product Key for Windows was previously attached as a label on the device. This key could be referenced for activation if the operating system needed to be reinstalled.
This is no longer the case with Windows 10 as the Product Key is stored on the computer motherboard. If Windows is reinstalled or reset and activated, no Product Key is required to be typed in as the key stored on the motherboard is automatically used when installing Windows.