Yesterday I have upgraded my Windows 7 SP1 to Windows 10 using Get Windows 10 App. After a while I found out that it can't activate it, it says error code: 0xC004C003 I've no idea why I can't activate my Windows 10. So I went back to Windows 7, and I want to install Windows 10 again as soon as I find out why it cannot be activated. - The first time I tried to upgrade to Windows 10, the installation failed at around 60% and went back to Windows 7, so I tried to uninstall some programs that may cause the failure (like SoftXpand, a program that can separate your PC into two workstations, each with its own keyboard and monitor) and unpluged unnecessary USB devices. - The second installation of Windows 10 was succesful. - My Windows 7 is genuine and activated. - I've made many hardware upgrades, but Windows 7 has always been activated after that. Does anyone know why my Windows 10 cannot be activated?