It looks like Microsoft is doing what everyone was trying to say “They would never do”. Forcing Windows 10 on us even if it’s not wanted. If you have Automatic Updates turned on and using one of the versions of Windows that qualify for the Free upgrade then your computer will download the 6 Plus gigabytes of install files for Windows 10. It will store it in a hidden folder until you are ready to install Windows 10. So if your Internet is metered it may end up costing you or eating up your data allotment. If you have a slow Internet connection, that connection may come to a crawl while the install files are being downloaded without you even being aware.
For more info and ways to remove and avoid the Windows 10 forceware, follow the link below.