It's the Windows 8 .1 Upgrade tip you've all been waiting for: The ability to download a Windows 8.1 ISO—a file from which you can make DVD- or USB-based bootable media—using your legally acquired Windows 8 (as in 8.0) product key. Thanks to everyone who wrote in with this tip via email, comments on this site, and Twitter. It's hard to know where the tip originated, but I want to be clear that this is not something I came up with personally, and this workaround is widely available on other sites and blogs as well. Here goes. As noted in Windows 8.1 Upgrade Woes , Microsoft provides a handy Upgrade Windows with only a product key page from which you can jump-start the Windows 8 or Windows 8.1 Setup from the web and optionally make an ISO file for later installs. But it inexplicably does not allow you to download the Windows 8.1 ISO—via Windows 8.1 Setup—with a Windows 8 product key. This doesn't make sense since Windows 8.1 is a free update ...