If you have a custom built PC then you'd need your own key. I don't think OEM's will activate on non OEM kit.
AFAIK they only started linking keys to hardware with Windows 10.
All this is very interesting for some however I will never update from W7 for what this pc is used for it buys me absolutely nothing.
This is news to me as I thought the WIn7 ->10 was all done now.