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This is Leela and I will help you with the question today.
Can you please confirm if your mac book supports windows installation? What is your mac book model?
Thanks for the details.
You can try installing windows 8.1 on your imac. Please check the link for more details.
You would need windows8.1 licence and I guess you have it.
Please check the site and let me know if you have any further queries.