Wait, so here is a question. When you say we have to surrender our previous OS installation, does that mean we permanently lose our ability to go back as in the Windows 10 activation cancels out your ability to reactivate your old OS, or does it just mean that you can go back but you'd have to wipe the drive clean and start over again? No, you can go back at anytime and reactivate just fine. I went from Windows 7 x64 to Windows 10 x64 back to Windows 7 x64 and Windows 7 will still activate just fine.