You are right, Photoshop can be used to manipulate photos. However, you should not take a photographer's integrity so lightly. First, check the photographer's website for his other photography. His name is Bud Kuenzli, believe it or not he is a real person and you can find many of his other aurora photographs here:
http://www.pbase.com/santa/aurora
Second, in order to manipulate that APOD into existence based solely on the Windows Vista wallpaper would be painstakingly difficult, especially considering the fidelity and resolution of the image you claim is the fake. Because I know exactly what processes one would have to go through in order to perform such a task, I can very easily say that it would be many times easier to actually photograph the aurora than it would be to create it.
Third, given the photographer's considerable portfolio, it is easy to see that he is the real deal and has a lot of experience photoraphing aurorae.
Fourth, there are no visible signs of manipulation other than the usual level and color adjustments that even the most amateur photographers do all the time. There are no mismatched textures, the perspective correct, there are no repeating textures, the grain is consistent throughout the image, and the stars themselves match up to their positions in the photograph (stars near the corners will be distorted by the camera lens).
Furthermore, there are too many inconsistencies between the two photographs for them to have even been taken in the same positions on earth, or for them to even be taken with the same camera settings. The grain is different, the terrain is different, the stars are different, the water is different, and the one you claim is the original is actually BLURRIER and of overall much lower quality than the Bud's image. Once someone manipulates an image, the result is inevitably of lower quality and shows many inconsistencies, not the other way around.
Indeed, one would have to be either insane or ignorant to make the accusations which you are making. I am going to give you the benefit of the doubt and say it is the latter.