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How to change file icon
http://www.vistaarticles.com/articles/542/1/How-to-change-file-icon
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Published on 05/1/2011
 
Vista presents an image of the document itself.

How to change file icon
Vista takes a new approach to file icons — the thumbnail-size images that represent your documents. Instead of using a single picture that simply denotes which application produced the document, Vista presents an image of the document itself. Open a folder and click the view menu and you have the choice of a number of different sizes that can help you identify the file you’re looking for.