maruniverse7 :
How is what i said completely wrong? You can still install windows 10 without a product key and add one later, thats what i did with my system
Completely wrong may be excessive.
However you didn't answer anything he asked
1. Do I need to buy it new?
2. Can I just use my drive with Win 10 on it.
rjroze Follow ThatVietGuy's instructions, to make sure your current Windows 10 is attached to your account, then you DO NOT need to buy a new Win 10 copy. Next your hard drive with Win 10 on it will not work, you need to download and reinstall Windows 10 because you're changing hardware. This is the only way you will get the best operation out of your new components.