what you are seeing is the plugin 'splash' screen, which is always shown when you are in design mode (you can't play in design mode).
To play something, you will need to add a target, either by setting the MRL property through the properties dialog, or by using the more complicated addTarget method in your VB code, as documented in this post
viewtopic.php?p=35906#35906
then you need to switch your form to user mode to play the MRL.
Since you only want to play MP3, you can set the Visible property to false, so that the plugin is hidden when your form is in user mode; however it will be visible in design mode.