Segundo a Microsoft, você não pode usar suas chaves do Windows 10. Você terá que chamar o Suporte de Ativação, fornecer prova de que você tem uma licença com direitos de downgrade e eles fornecerão uma resposta ao desafio de ativação que resultará em uma ativação única de uma instalação.
The downgrade process
Follow these steps to downgrade to an earlier version of Windows software:
- Use genuine Windows media and a corresponding product key for the version of Windows that is eligible for downgrade. The media/key should come from a previously licensed product from the OEM or retail channel.
- End users who are licensed separately through Microsoft Volume Licensing (VL) may provide their VL media and key to a system builder to facilitate the downgrade on their own systems.
- Insert the downgrade-eligible version of Windows media and follow the installation instructions.
- Enter the product key.
- If the software was previously activated, it cannot be activated online. In this case, the appropriate local Activation Support phone number will be displayed. Call the number and explain the circumstances. When it is determined that the end user has an eligible Windows license, the customer service representative will provide a single-use activation code to activate the software. Please note that Microsoft does not provide a full product key in this scenario.
- Activate the software.
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