It's comforting to know that it's not only Europeans who will be inconvenienced by installing Windows 7. Americans moving from a pre-release version of Windows 7 to the final version will also find it a pain in their comically over-sized rear ends.
That's because the upgrade versions of the Windows operating system (the cheapest way to move to the final version) check for a previous paid version of Windows on the drive. That means, if a user did a clean installation of Windows 7 on their test system (as recommended by Microsoft), that same user will have to back up their data, reinstall their original operating system (XP or Vista), then install Windows 7, restore their data, and then reinstall their applications.
For testers who were running XP, that means doing a clean installation of Windows XP over their Windows 7 test build and then a clean installation of Windows 7 over that. Vista users have the option of reinstalling that operating system and then doing an in-place upgrade or a clean installation of Windows 7.
Microsoft says that, for what it's worth, that's roughly the same thing that was required for those moving from pre-release versions of Windows Vista to the final release. In Europe, everyone will have to reinstall their OS, whether they've been using the pre-release versions or not, due to some mind-bending obstinacy on Microsoft's part.
Even so, it's an unfortunate burden for US users who have provided useful feedback and indeed been some of the operating system's biggest champions. Users were also pushed to do a fresh installation when moving from Windows 7 beta to the latest test version, although some users found ways around this.