How to Download Windows 10 and Install it Without a Key RELATED: First, you’ll need to. You can download it directly from Microsoft, and you don’t even need a product key to download a copy. There’s a that runs on Windows systems, which will help you create a USB drive to install Windows 10. If you aren’t on Windows, you can visit the to download an ISO directly (say, if you’re installing Windows 10 in Boot Camp on a Mac). If you visit that page on a Windows machine, it’ll redirect you to the download tool page instead. Just begin the installation process and install Windows 10 like you normally would. One of the first screens you’ll see will ask you to enter your product key so you can “Activate Windows.” However, you can just click the “I don’t have a product key” link at the bottom of the window and Windows will allow you to continue the installation process.