nd from then on you'll be able to access that commoon function we have always used: right-click an empty space of the desktop and choose the option Personalize of the contextual menu.
In the menu that appears you can change the wallpaper as usual.
In short, if you don't want to rack your brains to change the wallpaer of Windows 7 Starter Edition, install Starter Background Changer and do it as usual.