http://codefromthe70s.org/desktopearth_dl.asp
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Desktop Earth is a wallpaper generator for Windows. It runs whenever you're logged on and updates your wallpaper with an accurate representation of the Earth as it would be seen from space at that precise moment.
Images are created from high-resolution textures (2560x1280) so it's perfect for that QSXGA display - but they work on anything, even on SVGA.
There is an image for every month to accurately depict snow and foliage changes, and the night view is simply stunning.
The imagery is based on NASA's Blue Marble Next and Earth's City Lights.