Rich symbols are a powerfull feature of Fireworks. In the standard installation Fireworks have many ready to use symbols to design applications for the Web, Mac, Win and Flex. In this set of symbols you expand your library of symbols to design applications for Windows Phone 7. This symbols library supports automatic updating through Adobe Extension Manager.
When a MXP file is provided, just double click it. When there is no mxp file, just open the PNG file.