Movie Maker seems to be set to a widescreen aspect ratio by default.  When I import slides from a Power Point presentation in standard (4:3) ratio, Movie Maker automatically puts black bars on the sides to fill out the wide screen (16:9) ratio.  I want to produce movies that will maintain the 4:3 ratio since I am showing them with projectors that are set for that ratio.  How do I change the default to standard ratio?