Desktop/wallpaper problems, darn it

[qanda]This thread is about the Apple MacBook (white). Click here to see full specs[/qanda]I set my desktop for a picture of a dog:) I kept it for about a month than changed it:)(I have changed my desktop many times and am sure I did it fine):cool: but when I shut down my computer and started it up again later the desktop(wallpaper) image was the dog again:eek: :a I tried again-didn’t work:disagree: could the dog pic. be set as my default desktop image?:confused: how can I change that?:confused: please help me.:sad: I’m confused.:sad: this has never happened before!:sad: