I bought a laptop with Win10 installed. The main benefit of this OS was the startup speed. 5 seconds after turning it on I was able to use it, but lately it's taking far more time than it used to. Because of that, I'm willing to format it and install Windows 7. I'd like to know if someday, after install Windows 7 non-official, I can reinstall the original version of Windows 10? For what I've heard Win10 doesn't have a product-key and it's related to the motherboard, but I didn't understand how it works. I'd be thankfull if somebody could help me.