On a Vista machine, Windows 8 retains settings, user accounts and data files, but not applications. It's a partial upgrade.

From XP, Release Preview migrates only user accounts and files.

In one sense there's no upgrade path from either the Developer Preview or Consumer Preview of Windows 8 -- Microsoft says it's a "clean install" in that nothing, absolutely nothing, is saved -- but you should be able to retrieve files, like documents and images, by rooting through the "Windows.old" folder. Microsoft's documented the steps to do that in its own

Do I need a product activation key? Just as with the Consumer Preview, no you don't, at least if you use Setup to download and install.

You will, however, be asked for one if you install from a DVD or flash drive. The generic 25-character key -- it works for everyone -- is: