Windows 8 to Windows 7

You cannot use a copy of Windows 7 sold for use with a refurbished PC with a new machine. You would be breaking the EULA.

It looks pretty dodgy to me.

If I were you I'd save my money and convert Win8 to a slightly faster Win7 using Windows 7 Start Menu for Windows 8 which toggles off the Metro start screen and grafts on the exact same Win7 start menu, and 8GadgetPack - Gadgets for Windows 8.

These changes make 8 almost identical to Win7 but a little faster with some explorer improvements. You'll only need to go into Control Panel>Default Programs to replace the CrApps with your chosen Reader, WMP, Windows Photo Viewer, etc. If the crApps interfere further, toggle back on metro and uninstall them all.

If you don't have access to a Win7 disk to insert for the 7 Start menu graft then take a look at the popular alternatives http://www.classicshell.net/ or http://www.stardock.com/products/start8/

I would buy an OEM copy from newegg and skip the ebay nonsense.

Microsoft Windows 7 Home Premium SP1 64-bit - Newegg.com

That will be a full copy to install on one system.

7 has a perfect 5 egg rating there, and all the copies of 8 are 3 or 2 eggs, muhaha enthusiasts really hate 8.

I don't hate it, it's just not much of an upgrade, unless you have a tablet, and M$ should have known not to force a new desktop on the masses after all these years.

I can just imagine the horror at companies the day after the 8 migration.