How to change background on windows 7

Operating Systems & Open Source Windows
1

So I know how to actually change the background but I want to change the background on my school computer (which is heavily restricted). I was wondering if there are any other ways of changing it...

note: I'm not the best with windows 7 as I went from my mac to a pc using windows 8; although they seem to be quite similar.

2

I know it is non invasive but it is always better to not screw around with  schools PC's. They are probably locked down for a reason, or many.