Comment by JoshTriplett

See http://thenextweb.com/microsoft/2015/07/29/wind-nos/ ; "Windows 10 automatically encrypts the drive its installed on and generates a BitLocker recovery key. That’s backed up to your OneDrive account." Together with the ToS: "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 protect our customers or enforce the terms governing the use of the services."