...a new laptop, which is a windows 8 computer that came with windows 7 pro from the seller, via the downgrade rights option in windows 8.
If you are certain that the computer came with a license that has downgrade rights, you should be able to do a clean install of W7 Pro. You don't have to buy any retail copy of Windows. You can back up the token files like John advised and restore them after reinstalling. You wouldn't be able to download the ISO at the link John provide because OEM keys won't be accepted. Instead, you can follow this article to download an ISO from Microsoft Tech Bench. Once you have the ISO, head to MSDN Subsciber Downloads and search for the matching Windows version you downloaded. When you find the matching entry, click on the "Details" link to expand it. Use something like Hasher Lite to generate a SHA1 hash for the ISO and compare it with the one from MSDN. Once the hashes match, you know where to go from there.
Note: If the you computer is using UEFI, you have to follow this article to create a bootable USB drive.
Just in case, I would extract the key with ProduKey too.
Edited by Agouti, 08 April 2016 - 01:54 PM.