That is when you want to activate Windows 10, of course, a product key is needed. Activate Windows Defender on Windows 10.Best Tricks To Activate Windows 8 Permanently Offline.Best Ways To Activate Windows 7 Permanently Offline.How To Fix Windows 10 License Will Expire Soon.This is because the Windows operating system is closed source, unlike Linux which is open source. If you have not activated it, a watermark will appear that says “Activate Windows”. How To Activate Windows 10 Offline Permanently on Laptop PC Activation of Windows 10 Using KMS Auto-Lite