How to download and install Windows 8.1 for free

Windows 8.1 has been released. If you’re using Windows 8, upgrading to Windows 8.1 is both easy and free. If you’re using another operating system (Windows 7, Windows XP, OS X), you can either buy a boxed version ($120 for normal, $200 for Windows 8.1 Pro), or opt for one of the free methods listed below. To download and install Windows 8.1 for free, follow the guide below.

How to download Windows 8.1 for free

If you don’t want to wait for October 17 or 18, there are two options for downloading Windows 8.1: You can obtain a copy (and a license key) from a friend/colleague with an MSDN, TechNet, or DreamSpark (student) subscription, or you can download a Windows 8.1 RTM ISO from your favorite file-sharing website (The Pirate Bay, Mega, etc.)
While we’re not going to write a guide on how to obtain Windows 8.1 RTM from non-official sources, we will at least tell you to check the SHA-1 hash of the ISO that you download to make sure that it’s legitimate. If you hit up the MSDN Subscriber Downloads page, and then click Details under the version that you’ve obtained from elsewhere, you’ll find the SHA-1 hash. If you then use File Checksum Integrity Verifier (FCIV) on the ISO, the hash should match. If it doesn’t, assume the ISO has been compromised and download another. (But do make sure that you’re checking the right SHA-1 hash on the MSDN website; your ISO might be mislabeled).
The other easier, and completely legal, option is to download the Windows 8.1 Preview from Microsoft. It’s not as snappy as the final (RTM/GA) build, though, and has quite a few bugs/missing features. Bear in mind that if you go down this road, upgrading to a real version of Windows 8.1 will require a few more steps (discussed in the next section).

How to install Windows 8.1 for free

Once you have the Windows 8.1 ISO on your hard drive, the installation process is painless. Before you begin, you should consider backing up your important files and documents, but it’s not really necessary. You should also ensure that you have plenty of free hard drive space (20GB+).
If you’re already running Windows 8 and you downloaded the RTM ISO from somewhere other than the Windows Store, you can install Windows 8.1 by mounting the downloaded ISO in Explorer by double-clicking it, and then running the installer. If you’re on Windows 7, XP, or (bless your soul) Vista, you’ll need to burn the ISO to a USB thumb drive or DVD, or mount the ISO using a third-party virtual drive tool, like Magic ISO.
If you already have Windows 8, and you waited for the official release date, installing Windows 8.1 is as simple as visiting the Windows Store and downloading the free update.
In both these cases, the upgrade process should be very smooth, with your apps and settings fully preserved. If you upgrade from Windows 8.1 Preview, however, you will lose your installed apps, unless you first run a cversion.ini removal utility.
Once you’ve installed Windows 8.1, you should check out our extensive collection of Windows 8.1 tips and tricks, and be sure to check our Windows 8.1 review and hands-on impressions to ensure that you’re making the most of all the new features.