Change my acer notbook background

Hello,
(usually I would say hey with a ':)' instead of a ':(' but I am deeply upset.
On Thanksgiving I got a new laptop, I was super excited! It is a purplish pink Acer aspire one Intel laptop.
It has Windows 7 Starter.
I love this laptop,
But I have 1 problem....
My problem is that this laptop will not let me change my desktop background.
I've tried everything!! I went to control panel and typed in desktop background, but it found no results.
I went to a pic in my saved files and right clicked saying Set as Desktop Background, still nothing. The little box popped up saying, "are you sure you want to replace current background?" I click yes, and still, nothing. I downloaded a gadget background and still NOTHING.
any idea how to fix this? Because I am completely freaking exasperated on how to change it.
I NEED HELP!!!