I've ported Windows 7 explorer.exe to Windows 8 RP. That wasn't very easy and far enough from being complete, but result is working Windows 7 native desktop. Start menu pinning and MFU program list was chopped up completely from shell32, other things (search, all programs, system shortcuts customization, systray, desktop, taskbar, etc.) work. Metro isn't started; metro apps and UI don't work. Now tell me if this kind of thing is feasible for you. It requires explorer.exe and maybe couple of other files from win7. I'm planning to upload beta version soon; tell me which sites could be interested in this kind of thing.