Windows 10 Professional is a premium version of Microsoft's latest operating system. For Windows PC owners who do not have a working product key from the company, an upgrade will set them back US$199.

If your computer is no longer eligible for Windows 10 upgrade, it only takes an official Windows 10 ISO file to get your machine the Windows 10 Pro version without charge. This allows users to manually install or reinstall the OS for free.

Also read: Microsoft releases new criteria of 'highly secure' Windows 10 devices

The ISO image allows the creation of a bootable USB flash drive or DVD which will serve as an installation source. Hence, you will not need a Windows 10 product key to download the ISO media file from Microsoft.

However, users have to take note that a genuine Windows product key will be required for activation purposes during or after installation.

Windows 10 Pro criteria

Before moving forward, take a look at these criteria that Microsoft has set:

  • Reliable internet connection
  • Enough memory storage in your computer
  • An empty USB storage device or DVD with at least 4 gigabytes of space
  • DVD burner, if you are going in that direction

If you choose to clean install your computer, refer to this Microsoft page. You can check all other Windows 10 system requirements via this Microsoft page.

Install Windows 10 Pro without product key

To install Windows Pro, here is a simple guide on how to do it. This also works for Windows 10 Fall Creators Update.

Step 1: Go to Microsoft's official Windows 10 Disc Image (ISO) download page.

Step 2: On the drop-down menu, choose Windows 10.

Step 3: On another drop-down menu, choose your preferred language.

Step 4: Choose between 32-bit and 64-bit according to your computer system's processor. Click on the compatible software version.

That's all you need to do to upgrade your computer's operating system to Windows 10 Pro. Don't forget to share this with your friends and family!