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#11
You don't wanna do that as Windows 10 licensing apparently is tied up to the hardware. That will just end you up with 2 licenses locked to 1 machine. But you can transfer it and call MS for re-activation on different machine.
If you need a second copy on the same machine, you can just try cloning it. I am not sure, maybe someone can also enlighten me about this, if Windows 10 licensing is also now tied up to a hard drive because it's not the case with Windows 7.
So basically, you don't wanna waste the retail copy of your Win 7 if you are planning to build another machine in the future. But then again, it's still transferrable but requires some extra legwork with MS.