I recently purchased a used SFF PC running windows 10 pro and I made an install disc using the software that comes on the PC. I then upgraded 2 older Think pads with new SSDs and installed the windows 10 pro onto them. It never asked me to enter a license code or anything but just automatically registered authentic through my Microsoft account. How is this possible? I believe I cloned my original PC because when I change my desktop background on the original PC it also changes the background on the 2 think pads as well! I can change the background on the laptops to something else and it doesn't change it on the original PC.