For some reason, I can't change the desktop picture on my Dell laptop. If I go to the desktop, click properties and try to change it, the options are basically frozen. If I go to a web page and choose a picture, right click and then choose "set as background" it doesn't change it. It remains just a blue background. I can't even change the color. When I then restart my laptop, I do see the picture that I chose from the web page momentarily, but then the regular old blue background comes up. What's up?