Once you’ve obtained a legitimate copy of Windows 8.1 via ISO (tutorial here), how do you manually upgrade your existing copy of Windows 8?
Like obtaining the Windows 8.1 ISO in the first place, Microsoft doesn’t have a direct way of manually upgrading. If you’ve found yourself having issues updating via the Windows Store app, as I did, this is what you’ll want to follow (manually upgrading also fixed a few other problems that I was previously experiencing; doing a clean install wasn’t practical). It’s not as straightforward as booting up the Windows 8.1 installer and choosing an upgrade install.
Step 1: Accessing the Installer
Now that you have a Windows 8.1 ISO, there are a few ways in which you can go about upgrading your existing Windows 8 installation. One method is by mounting the ISO from within Windows itself. You can do this by right-clicking on the ISO file, going to Open with, and choose Windows Explorer. It should now appear on your computer as if it’s its own DVD drive. You can run the installer by running the setup.exe file and follow the steps.
Another, more traditional way is by “burning” the ISO file to a USB drive, or burning it to an actual DVD. The former requires a USB drive that’s at least 4GB in size. Chances are you have one somewhere. It also requires that the flash drive be erased before the process begins. Regardless of which you choose, you can do so via Microsoft’s free “Windows 7 USB/DVD download tool.” Simple download it, install it, and run it. The rest of the steps are self-explanatory. After that’s finished, you can boot from the USB drive or DVD directly. Refer to your motherboard’s manual to figure out how to boot from other discs/drives if it doesn’t boot from it automatically. The key to use is commonly F10, F12 or DEL.
Step 2: Installing Windows 8.1
Now that you’re in the installer, you can go through the initial screens. Once you get to the part about the key, type in your original Windows 8 key. You’ll notice that it will fail to work. This is because Windows 8.1 is designed to be installed using 8.1-specific keys. Why Microsoft decided to block Windows 8 keys, nobody knows, but considering 8.1 is a free update for existing 8 users, it continues to make no sense.
Instead, you’ll need to use the following generic key: XHQ8N-C3MCJ-RQXB6-WCHYG-C9WKB Continue to install an upgrade copy of Windows 8.1 afterwards.
Step 3: Activating Windows 8.1
Since we had to use a different key to at least get Windows 8.1 upgraded, we’ll now have to swap that key out with your original, hopefully legitimate Windows 8 key.
To do this, open an elevated Command Prompt window, which can be done by pressing WinKey+X, followed by A. Type in the following, replacing the Xs with your key:
slmgr -ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
After hitting enter, your computer should instantly be activated, just like on Windows 8. You can verify this by doing WinKey+X, then Y. At the bottom of the window, it should say that you’re activated. If not, go ahead and reboot.
And that concludes it. You’ve now manually upgraded your existing copy of Windows 8 using a copy of Windows 8.1.