We will access, disclose and preserve personal data, including your content (such as the content of your emails, other private communications or files in private folders), when we have a good faith belief that doing so is necessary to.
Source: Windows 10 is possibly the worst spyware ever made
The tactics Microsoft employed to get users of earlier versions of Windows to upgrade to Windows 10 went from annoying to downright malicious. Some highlights: Microsoft installed an app in users’ system trays advertising the free upgrade to Windows 10. The app couldn’t be easily hidden or removed, but some enterprising users figured out a way. Then, the company kept changing the app and bundling it into various security patches, creating a cat-and-mouse game to uninstall it.
Source: With Windows 10, Microsoft Blatantly Disregards User Choice and Privacy: A Deep Dive | Electronic Frontier Foundation
And while users can disable some of these settings, it is not a guarantee that your computer will stop talking to Microsoft’s servers. A significant issue is the telemetry data the company receives. While Microsoft insists that it aggregates and anonymizes this data, it hasn’t explained just how it does so.
Anti-Beacon is small, simple to use, and is provided free of charge. It was created to address the privacy concerns of users of Windows 10 who do not wish to have information about their PC usage sent to Microsoft. Simply clicking “Immunize” on the main screen of Anti-Beacon will immediately disable any known tracking features included by Microsoft in the operating system.
Source: Spybot Anti-Beacon for Windows