Windows 8 Pro Upgrade version - getting it to work

[Virumo]

So, I've got Windows 8 Pro Upgrade on the way. I currently have Windows 8 Home OEM installed on my machine. I have a Lenovo Y410P, and taking the 'no survivors' approach to bloatware, I downloaded and made a DVD backup of Windows Home OEM, and reinstalled it. At no point was I prompted for a license key, it used the one that's embedded in my system (I think this is what sets OEM versions apart). Once Pro arrives, how will I get it to activate?

 

[Wolfpup]

Wait, is that legal (like official) that MS offers some clean install you can download like that? If so how do I do that? I'm not entirely clear how to make restore discs at all in 8, much less do a clean install without paying for a new OS (I guess a full Pro disc would be able to do a clean install...one hopes).

I'd assume that upgrading from there would just work like normal, that you'd be able to do a clean install if you want, and just punch in the activation code from the Pro Upgrade?