I've spent way to many hours looking for software to do the following simple task, so now I'll ask.
I need software that will open an image and put a 'crop box' on it. You can set the 'crop box' to standard screen resolutions (1024x768) or define a custom one. You can move the 'crop box' around on the image to select the area you want. You can re-size the 'crop box' (selecting a corner and dragging w/mouse) and it maintains the correct aspect ratio. You can save the area in the 'crop box' to use as the Windows background. (The software doesn't need to set it as the background, I can do that myself in Windows XP.)
The free software sites (CNET.com, etc.) have lots of image editing software that do things much more complicated than this simple task. I've spent too many hours downloading them to see if they will do this particular task. The ones I've tried would require manual trial and error to get the part of an image that I want saved as an image, with the correct aspect ratio so Windows doesn't screw with it (stretch, tile, crop) when I select it as the wallpaper.