Windows 8.1 Preview provides a first look at Microsoft's free update for Windows 8. It's not yet finished - for "Preview", read "Beta" - and can't be uninstalled if you have problems, so most people will be better off avoiding it for now. But if you're interested, there's plenty to explore.
Microsoft has tried to address some of the most common Windows 8 criticisms, for instance. You can now optionally boot to the desktop. A Start button can return you to the Start Screen, or launch the Apps view, for a sort-of Start Menu-like experience. And you can disable the Charms bar, or the hot corners.
There's now more control over how Windows 8 apps are displayed, too. Apps can be automatically arranged side by side, resized to suit your needs, and at best you can now have up to four apps on the screen at once, and change the size of each window (although the latter apparently requires "at least 2560 pixel width on a 24" or larger monitor", which we would guess is going to exclude a lot of people).
The update comes bundled with Internet Explorer 11 (it's reportedly faster, and allows you to browse tabs side by side), as well as a Settings app which is a Start Screen equivalent (almost) to Control Panel. There are several lesser new apps (SkyDrive, Calculator, Alarm, Fresh Paint, Bing Food and Drink, Bing Health and Fitness), while other apps have been updated (Mail, Calendar and others), and a redesigned store makes it easy to find more apps you might like.
Elsewhere, Search has been improved and is easier to access; tethering support allows you to turn your PC into a wireless hotspot; you're now able to customise the Lock screen with your own images; and the Start Screen offers more options for tile sizes, and new ways to arrange them.
How to get Windows 8.1, then? If you're interested, the simplest way is to download and install the update, restart your PC, and follow the notification prompt to go to the store, then download and install the full Windows 8.1 package.
Please note, if the update gives you an error message saying "the update is not applicable to your computer", then this most likely means your PC isn't using one of the languages supported by the Preview. Right now that's only Arabic, English (US), Chinese (Simplified), Chinese (Traditional), French, German, Japanese, Korean, Portuguese (Brazil), Russian, Spanish, Swedish, and Turkish.
There may be workarounds for this - you could try changing your locale, for instance - but Microsoft warns: "if you install Windows 8.1 Preview in a language that's different from the language currently on your PC, you can only keep your files, not your apps or settings". We would recommend you don't try to bypass the "not applicable" error unless you know what you're doing and your system is fully backed up.
This is the English (US) 64-bit version supplied as an ISO image. Simply download the ISO, double-click and run 'setup.exe'. Product key: NTTX3-RV7VB-T7X7F-WQYYY-9Y92F
An interesting collection of updates which offers significant improvements to Windows 8. It's unfinished and there's no "uninstall" option, though, so only try it if you've a backup available