Genuine Windows operating system is published by Microsoft, properly licensed, and supported by Microsoft or a trusted partner. Only genuine Windows customers have access to all optional updates and downloads available from Microsoft, which are designed to help you get the most from your PC.
Activation pairs your product key with your hardware configuration and helps verify that your copy of Windows hasn’t been used on more computers than the Microsoft Software License Terms allow. Usually, you need to activate Windows only once, unless you make a significant hardware change.
Genuine Windows, however, is a recurring process that checks your product key to make sure it’s not blocked or being used on hardware that’s different than what you were using when you activated Windows.
The genuine, or validation, check is performed when your computer attempts to download optional updates from Microsoft. For example, when your computer downloads updates, Windows checks to see if your product key is valid. If it is, Windows on your computer is genuine, and you’re eligible to receive the latest updates from Microsoft. If it’s not, your computer is running non-genuine Windows.
The best way to know is to make sure to buy Windows or a PC with Windows preinstalled either directly from Microsoft or from a local or online retail store that you know and trust.
For other ways to check if you’re running genuine Windows, visit the What to look for page on the Microsoft How to Tell website.