If I install Windows 10 and get the automatic updates from Microsoft and then after a while ( a month,a year...) I decide I don't like it,can I revert back to my original Windows 7?
I suspect I'm being rather too pessimistic, but I don't what to get 'caught-out' somewhere down the line by T&C's that I didn't read.
Thanks
You could take an "image" of your hard disk as it is now and save it on an external hard drive.
Then when you upgrade to Windows 10 you will still have a copy of your computer software as it was when running Windows 7 so you can just restore your hard disk from that image if you don't like Windows 10.
I use Macrium Reflect Free Edition to take an image of my hard disk but there are other products that can also do it.