So i purchased a refurbished Dell laptop, and it came with a windows activation key for Windows 7 Pro 64 bit. I then activated windows using the key and everything was fine. After a couple of weeks, I was given the option to update to Windows 10, and i did. Well Windows 10 has the ability to easily go back to Windows 7 if you dont like it... for 30 days after installation. the 30 days have passed, and now i'm starting to have some really big problems with windows 10 and i want to go back to windows 7. i have a Windows 7 Pro 64 bit installation CD, but i need to know if the Windows activation key i got originally would still work.