how do i change the background on my mini acer notebook?

kay so I have my laptop to Weihnachtenund I have no idea how to verändern.wenn to the background on them, I preview an image and then the right is, there is no cause, “says set as Desktop Background” and If I set the right mouse button on a picture on the Internet, there is something that says, “as desktop background”, so I click it, but nothng passiert.Hilfe please:)

I’m Having Trouble Changing My Computer Background?

So I have a mini Acer Notebook. I have no idea how to change the background. yes, I have tried right clicking it and saying “Set as desktop background” but it doesnt work. and saving it, but when i right click on the desktop, it doesn’t have a normal properties bar. I am using windows vista.. any help!