Migrate Win7HP -> Win8Pro -> Win7Pro ?

Hello guys, I'm running Windows 7 HP OEM and plan to upgrade to Win7Pro, mainly due to domain connect possibility. Is it formally and technically possible to do a trick: First, upgrade from Win7HP OEM to Win8Pro OEM (using the offer for 39,99 USD: http://windows.microsoft.com/en-us/windows/buy ), and next, downgrade from Win8Pro to Win7Pro? That’s because it would be a cheaper way than...