What specific installation media or DVD is needed to reinstall Windows 7?

For example:
I have the Windows 7 product key on this <span class="qlink_container"><a href="/Lenovo">Lenovo</a></span> laptop.
Do I need the Lenovo OEM DVD?
Or can I use the downloadable ISO file, then burn to a DVD, or preferably copy to a <span class="qlink_container"><a href="/Flash-Drive">Flash Drive</a></span>?

Why have you copied a question that was posted years ago on another I won't waste my time answering it…

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