With Windows 8 arriving in public form on October 26, millions of users are still running the Release Preview version of the operating system are wondering what their options are: Can they upgrade? Or will they need to start over again from scratch?

I asked Microsoft about this issue way back in late May, when I had my second Release Preview briefing. At the time, I was told that Microsoft had not typically supported upgrading from near-final versions of Windows (the Release Preview would have been tagged as a Release Candidate, or RC, in previous versions) to the final version. That said, they were looking into doing something for users, would perhaps support migrations. (Which I’ll explain in a moment.)

Microsoft wasn’t being coy. They really weren’t sure at the time what they could support, and didn’t want to set unrealistic expectation. But given the sheer number of people using the Release Preview, it’s notable that they’re supporting this at all.

You may recall from previous articles, or from Windows 8 Secrets, that Microsoft has changed the way they describe the processes by which we move from the one version of Windows to the next. In the past, we used the following terms to describe the different ways in which you could install Windows:

Clean install, where you install—or reinstall—Windows from scratch.

In-place upgrade, where you upgrade to a newer version of Windows from within the older version, retaining most of your settings and applications, and all of your documents and other data files.

Migration, by which Setup backs up your settings and/or data first, then clean installs Windows, and then reapplies your settings and/or data to the new OS.

In Windows 8, these types of installs can all still occur, though they’re not all available in all circumstances. More important, Microsoft has significantly changed how it communicates these choices in the Setup user experience.

That is, if you run Windows 8 Setup from within a previously supported version of Windows—Windows XP with Service Pack 3 (SP3), Windows Vista, Windows 7, or, yes, the Windows 8 Release Preview—the choices you get will vary from OS version to OS version. These choices appear at a stage of Setup called Choose What To Keep, which occurs right after you agree to the End User License Agreement (EULA).

While there are four possible choices, depending on the OS from which you’re starting, you will only see two of them if you run Windows 8 (RTM) Setup from the Windows 8 Release Preview. And these choices indicate that Microsoft has, indeed, elected to support a minimal migration from the last pre-release milestone of this system to the final version. Those choices are:

Personal files. Here, any documents and other files that are stored in the Users folder (C:\Users\ by default) will be carried forward to the new install. So you will lose installed Metro-style apps (though you can get them back easily enough by signing in to the same account in RTM and visiting the Windows Store), installed desktop applications (which you’ll need to manually reinstall), and any OS, app, and application settings (though many system-level settings are synced through your Microsoft account if you are signing in that way as recommended).

Nothing. Here, nothing is saved, and Setup will perform a clean install.

choose-what-to-keep

So there you go: Microsoft does support a minimal migration from the Windows 8 Release Preview to the final, shipping version of Windows 8.

Should you take advantage of this feature? Honestly, if you’re using a Microsoft account to sync settings already, and have configured the SkyDrive desktop application to reconfigure your Windows 8 libraries already and store important documents and other data files in the cloud, you may be better off just doing a clean install. Of course, you perform either of these install types at your own risk, and be sure to back everything up ahead of time either way.