Just curious, why do you have to "downgrade?
I'm trying to keep all the licensing of Windows 7 legal. We have four computers in the house. Currently mine is the one with Win 7 Ultimate. I have ordered the 3 pack of Windows 7 Home Premium(HP) online with physical media. There can only be one PC in the house with Ultimate on it. I want one of the kids, who can make use of more features in Ultimate, to have that for their computer. I can get by fine with HP. I want to be able to make the transition to HP when my order arrives.
All of them are going from XP Pro 32 bit to 64 bit versions of Windows 7. They are going to have to do a complete reinstall of everything anyway. Plus, I am the only one of the four PC's using Acronis True Image Home 2011 for back-ups. Everybody has their own favorites for antivirus, back-up, and so on.