This command is just a shortcut to the Default Programs control panel.
It has two functions:
To let you specify which program (not necessarily Microsoft's) you want to use as your Web browser, email program, instant-messaging program, Java module, and music playera choice offered by Microsoft to placate the U.S. Justice Department. Details are on page 226.
To specify which program opens when you double-click a certain kind of document. For example, if you double-click a JPEG graphic, do you want it to open in Photoshop or Windows Photo Gallery? Details on page 223.
Note: Windows veterans may want to note that this file-association function used to be called File Types, and it was in the Folder Options window.
Default Programs: All Versions 
