Win7 is a good system. At some point it will no longer be supported, but right now it's fine.
I dreaded switching to Win10, and put it off for a while. My daughter accidentally turned on the "automatic" upgrade on my desktop. Turns out it was a non-event. I deleted some of the tile things that show up beside the start menu, and the start menu looks a little different, but otherwise no big changes. All my taskbar buttons and files are intact.