There are all kinds of questions and answers relevant moving Windows 8 to a new hard drive. I'm not seeing anything quite applicable to my situation.

I have a new, unopened, unbooted notebook with pre-installed Windows 8. I will be replacing the hard drive before ever booting, unless that is not possible for some reason. I want to "downgrade" to Windows 7 Pro, and I want a clean installation. To do so legitimately, I apparently either need to:

1. Upgrade Windows 8 to Windows 8 Pro using Windows 8 Pro Pack, then downgrade; or
2. Just install a newly-licensed copy of Windows 7 Pro.

(Let me know if I've missed an option.)

Installation media is likely not a problem, though if I need something vendor-specific that I cannot otherwise download, that could present an issue (Asus notebook, if that matters). If I could, I would just buy the Pro Pack upgrade, swap the hard drive (without ever booting), then install Windows 7 Pro directly on the new hard drive, using the Pro Pack key for activation. Will this work? Are there any activation issues?

Edited to clarify, as some comments and answers indicate confusion:

Here is, ideally, what I want to do:

1. Before ever powering on the notebook, remove the current hard drive.
2. Replace this hard drive with a new, blank hard drive.
3. Install a clean copy of Windows 7 Pro on this new, blank hard drive.

Unless I have no choice to accomplish the end result (a clean install of Win7 Pro on the newly-installed, previously-blank hard drive), I am not wanting to:

1. Install Windows 7 "over" the current Windows 8 install (after upgrading to Win8 Pro). That would involve using the currenly-installed hard drive. I want to use a new, different hard drive.
2. Copy the Win8 install to the new hard drive, then install Windows 7 "over" that installation.
3. Install Windows 7 "over" the current Windows 8 install (after upgrading to Win8 Pro), then copy the installation to the new hard drive.

If I have to use one of those three options, I will, but only if there is no other choice. Please note that this question is not about licensing: I will purchase the necessary license(s) to accomplish this procedure legally (apparently either Win8 Pro Pack or Win7 Pro -- the former currently appears less expensive).