When the associated file is double clicked it will be handled by a single instance of your application.This lets your application act like Media Player rather than Notepad.

Each time you double click a media file Media Player does not open a new window but re-uses the existing one.This is normally difficult to achieve in Visual Basic but the One Only control makes it simple and also allows you to create the associations between file types and your application.Extending the association allows you to add items to the right click pop-up context menu for your associated file types as well.