Check the program's properties setting, in the 'Shortcut tab you should see
a 'Run' option with a pull-down list to allow you to select the Window size.
JS
I have the same question, after having already set the run option in properies to minimize some time ago, but it made not the slightest difference, and the program still starts in a normal window. Spent hours looking for this solution. Several attempts to get help from microsoft but they don't want to know, they keep transferring me away to sources that i've already established cannot or will not help