Microsoft is reportedly downloading Windows 10 installation on Windows 7 and 8.1 computers even if users have not opted into the upgrade. Microsoft admitted that it was downloading the unwanted files on users’ computers. Microsoft is not only consuming your storage space but also using your Internet bandwidth for unrequested files, as the Windows 10 installer downloads up to 6 gigabytes. Microsoft said in a statement: “For individuals who have chosen to receive automatic updates through Windows Update, we help upgradable devices get ready for Windows 10 by downloading files they’ll need if they decide to upgrade”
Source: https://thehackernews.com/2015/09/microsoft-windows10-download.html