How to restore my Win 7 Vista computer?

I have a Win 7 Vista Lenovo Thinkpad T61 from some company that came without an operating system and all that, my question is, how do I get/put Windows 7 Vista Business on this laptop somehow because I don't have an os disc, but I do have a product key for this os.

additional info: I currently installed Windows 7 Home Premium using an Acer restore disc that I made earlier that didn't require an os product key, and now Windows is telling me: "this copy of Windows is not genuine"
thank you

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