so Here's the deal.I'm building a new pc and I'm going to use my existing hdd from my previous pc 500 gb sata which already has windows xp on it.I want to install windows 10 rep the new pc after I plug it in.I have downloaded the free iso file and im planning to buy a jeycause xp users won't be able to use Windows 10 upgrade for free.So will my windows install properly and will they require a key during the installation of can we skip it for later.