If you have ever used Windows 7 Starter Edition, you'll probably know that you can't change its wallpaper directly by right clicking and then choose properties. In order to change Windows 7 Starter background wallpaper, you need to use third party software to do that.
In fact, when you go to search at google, you'll also find lots of such freeware to download in order to do this task. Here's a video teaching you how to change Windows 7 Starter background wallpaper, along with a link where you can download the freeware for that task.