There are a few ways you can still get Windows 10 for free, without using a pirated license: you can install Windows 10 with a 7 or 8 key, or install Windows without a key—it will work just fine, save for a small watermark reminding you to purchase a license.

Here’s how each of those methods work.

Provide a Windows 7, 8, or 8.1 Key

Windows will contact Microsoft’s activation servers and confirm the key to the previous version of Windows is real. If it is, Windows 10 will be installed and activated on your PC. Your PC acquires a “digital license” and you can continue using and reinstalling Windows 10 on it in the future. If you head to Settings > Update & security > Activation after installing Windows in this way, you’ll see the words “Windows is activated with a digital license”.

Microsoft hasn’t communicated what’s going on here, or whether it will block this method in the future. But it still works right now. Even if Microsoft blocks this trick in the future, your PC will keep its digital license and Windows 10 will remain activated.

Reinstall Windows 10 if You’ve Already Upgraded

To do this, just download the Windows 10 installation media and install it on that computer. Don’t provide any key during the installation process. It should automatically activate after it contacts Microsoft’s servers.

Sure, you can only do this if you’ve already upgraded to Windows 10, but you can continue to install Windows 10 for free on the same computer in the future–even if you replace its hard drive or other components. The new activation wizard in Windows 10’s Anniversary Update will even help you troubleshoot hardware changes and reassociate the digital license with the correct PC.

Skip the Key and Ignore the Activation Warnings

Windows 10 will keep nagging you to activate it and won’t allow you to change any of the options under Settings > Personalization, but otherwise work just fine. It’s not something you’d necessarily want to do on your main computer, but it’s a very convenient way to set up a quick virtual machine, test Windows 10 on a PC, or install Windows 10 in Boot Camp. You can even pay to upgrade to a legal, activated version of Windows 10 from within your unactivated Windows 10 system after installing it.

This isn’t technically allowed by Microsoft’s guidelines, but they’ve specifically designed Windows to work this way. If Microsoft doesn’t want people doing this, it’s free to change Windows to block this in the future–and it might. But Windows has worked this way for years. This was even possible with Windows 7.

You can also head to Microsoft’s website and download a 90-day evaluation version of Windows 10 Enterprise. It will continue working for 90 days–about three months. It’s designed for organizations to evaluate Windows 10 Enterprise.