To me the simplest and easiest way is to get a good backup/restore program and set it up to make periodic full system backups. I use Easeus Todo Backup Free which is free for home use. A lot of folks here on BC use the Macrium program, and there are many more. You just install one of these, set it up to make the backups automatically when you want, and it will do the rest automatically.
If you just back up your data and then restore to factory settings, you have to redo all the tweaks you've made to Windows (including email setup and contacts, browser favorites, taskbar icons, etc. etc.), reinstall your programs, and copy all your data back when the need arises. That can take a whole lot of time and effort. With full system backups, you can be back up and running in 30 minutes.