It's possible to download the Windows 8.1 ISO file using your Windows 8 product key
If you remember Microsoft said that it wasn't in its plans to release the ISO file for Windows 8.1, but as it turns out you don't have to wait until the company changes its mind, you can download the ISO version of Windows 8.1 using your Windows 8 product key.
Here is how:
- Go to the Windows 8 upgrade page
- Download the "Install Windows 8" assistant
- Enter your product key and as soon starts downloading, close the installer using the X button in the top-right corner.
- Go back to the Windows 8 upgrade page and now download the "Install Windows 8.1" installer
- Now simply double-click it and you'll see that Windows 8.1 will start downloading.
Hope this is helps anyone who wants to install the new operating system from scratch.
I have a more detailed version of the guide here: http://pureinfotech.com/2013/10/19/download-windows-81-iso-using-windows-8-product-key/