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If the Windows 7 that you had on your computer was activated, there is no need to activate it again. It will not ask for activation.
If it is asking for activation key you have to revert back to Windows 7, check if it is activated, and if it is not activate using the Windows 7 key, and then upgrade it again to Windows 10. No Windows 7/8.1 key will work Windows 10.
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