Users that don’t want Windows 10 will get it anyway, Microsoft gradually downloads the new operating on Windows 7 and Windows 8.1 systems. The files then reside in a hidden folder waiting till the user decides to upgrade. The files are downloaded through Windows Update and according to Microsoft they are downloaded to make it faster to upgrade to Windows 10
The website The Inquirer reports about users complaining about slow internet connections or connections with a data cap. The first found their connection to be slower than usual and the latter was surprised to find that they exceeded their limit.
Microsoft acknowledges that Windows Update not only downloads updates for the currently installed OS, but also silently downloads parts required for the installation of Windows 10. The company argues that it saves download time when an user decides to upgrade.
Even if users never wanted to update, they are force fed the files which take up several gigabytes. The Windows 10 files are downloaded to the folder $Windows.~BT which can take up 3.5 to 6GB.