Downgrading to Windows 7 from 8

I had a general question regarding OEM computers that come pre-loaded with Windows 8.  I always thought that with previous version of Windows, that you could legally downgrade to the previous version of Windows.  Maybe it's because I typically work with business pc's (Dell/Lenovo's) and they seem to always have the option to pick either the latest or previous version of Windows.  A friend recently bought a brand new Dell Inspiron desktop that came with Windows 8.  I know how to change all the hard drive modes back to AHCI and install Windows 7 for him, and I have DVD's of all the versions of Windows 7.  The problem is, once I downgrade it to 7, I am not sure how to activate Windows.  I figured Dell would tell me how to do this, but after chatting with Dell support, I was told that I am allowed to downgrade, but I have to buy a copy of Windows 7.  So basically, my friend is paying for a copy of Windows 8 and wasting it by installing Windows 7.  I was surprised that Dell didn't offer an option like I thought they did with their business class machines (maybe they don't even offer it with their business class machines, but I am pretty sure they do).  On top of all that, this Inspiron desktop didn't even come with a Windows 8 COA sticker with the "key" printed on it.  The support agent said in order to get a Windows 8 code, I would have to call into the tech support phone line and ask them for it.  This is all very different than it used to be and just very frustrating.  Is there possibly a way to "turn in" or exchange the copy of Windows 8 that came with this Dell to Microsoft and get a valid Windows 7 key or will they turn me away too?  Why does Microsoft and Dell do this to the end users?  Why do they insist on keeping us from using the OS we want to use?

By the way, I am trying to stay away from the whole debate of "just go to Windows 8...it's a small learning curve" type of thing.  I've already advised my friend to just go with Windows 8, but he wants 7...regardless of my recommendation.  From an IT perspective, I am just trying to understand how and why Windows activation and OEM's work these days.

One last question...if Dell says I have to buy a copy of Windows 7 in order to get it legal on this desktop, where can I buy a real copy?  I heard that Microsoft doesn't sell Windows 7 anymore.  I am sure there are plenty of 3rd party vendors that still sell it, but what is the Microsoft/Dell recommendation here?