“Attention, human!
“We are Microsoft and we own your computer...”
Technically they own the software. You purchase the right to use the software this is what is meant by the End User Agreement (EULA). People tend to overlook this fact because they paid for a disk in which comes with software and install it on their system. Since it is their system they believe everything on it is theirs. Unless the end user coded the software under their own name, no software is owned by the end user.
Thus Microsoft owns Windows on each machine.