Microsoft has taken the choice away from the user, wether or not they want Windows 10 - so if automatic updates is enabled, then Windows 10 will be downloadet and installed - and there is nothing the user can do to stop it.
The user just have to wait until the install is finished and then its possible to go back to previous windows version. windows 7 is supported until 2020.
The free Windows 10 update run until juli 2016, and after this period you have to pay for Windows 10.
Personally, I do not recommend people to update, since Windows 10 has too many errors and bad updates that often break something in Windows, And its not even certain that you PC can run Windows 10 100%. There can be drivers that do not work as they should, - even though Microsoft claim the opposite (do not trust the update program).
If you want to transfer to Windows 10, then its better to invest in a new machine or wait for the hardware manufacturers to make new drivers - for some products you can use the old Windows 7 and 8 drivers, but its not always they work as they should together with Windows 10(Microsoft's fault, not the driver).
Or there are the possibility to go down to your local computer guy and get your machine checked to see if there should be drivers for windows 10, so you can upgrade now.
Personally, I skipped this and installed Peach OSI on my laptop - I'ts fork of Ubuntu Linux, based upon an heavily modified Xubuntu. So far I have had no complaints, of course there are a few things that needs to be modified to fit your machine and you, but most things worked out-of-the-box.
I will later make a review of Peach OSI on my laptop, with pictures.