Windows 8.1 Preview screen

We show you how to create a bootable USB flash drive from which you can install or upgrade Windows 8.1.

Windows 8 users can upgrade to version 8.1 free of charge via the Windows Store, but if you have several PCs and laptops this means downloading a multi-gigabyte file for each one. If you'd rather only download this once, or perform a clean install of Windows 8.1 without having first installed Windows 8, then Microsoft makes things difficult – although the update is free for all users of Window 8, you can't install it with a Windows 8 product key.

Thankfully there are workarounds that'll let you download a .iso file just once, and this can then be used to create a bootable USB flash drive from which you can install or upgrade Windows 8.1.

First, you'll need to download a .iso file containing an image of the Windows 8.1 installation medium from tinyurl.com/92bxels. Select Install Windows 8, run the setup program and enter your Windows 8 product key when requested. It will then offer you a download of Windows 8. Click Next, wait for the download to start, then quit the program to abort the download. Now go back to the Microsoft web page and select Install Windows 8.1. This will download another setup program, but for Windows 8.1. Run this and it will start to download the Windows 8.1 .iso file.

If you omit the steps above to start the Windows 8 download, you'll be prompted for a Windows 8.1 key and won't be able to start the download with your existing Windows 8 key. Starting off the download of Windows 8 causes the Windows 8.1 downloader to skip the product key request.

Once the download is complete, you can choose to create a bootable flash drive directly, though, we recommend the ISO file option as you can use this with the Windows 7 USB Download Tool (available from tinyurl.com/mry6yqd) to create as many USB flash drives as you wish.

After you've created your installation medium, you'll need to make a small modification in order to prevent the installation requesting a Windows 8.1 product key when you launch it. Open Notepad and create a file containing the following lines:

[Channel]
Retail
[VL]
0

Save this file with the filename 'ei.cfg' in the Sources folder on your USB flash drive. You'll now be able to install Windows 8.1 from this drive, which will allow you to skip entering the product key. Once Windows 8.1 has been installed, you'll then be able to activate it with your existing Windows 8 key.

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