The MainFormOnTaskBar property controls how Windows taskbar buttons are handled by VCL. 

If the property is true, a taskbar button represents the application's main form and displays its caption. If false, a taskbar button represents the application's (hidden) main window and bears the application's Title. 

MainFormOnTaskBar must be true to use Windows Vista Aero effects. These include live taskbar thumbnails, Dynamic Windows, Windows Flip, and Windows Flip 3D. 

If a change to default behavior is required, MainFormOnTaskBar should be set in the .dpr file after Application.Initialize and before main form creation. The MainFormOnTaskBar setting is intended to persist for the life of the application; later runtime changes of this property could result in unexpected behavior. 

MainFormOnTaskBar defaults to True for applications created in Delphi 2007 and later products and False for earlier products. 

The property can be applied to older applications. Note that it affects the Z-order of your MainForm in case your application depends on this.  

To update existing VCL applications, add the following line to the project's .dpr file after Application.Initialize;:

Application.MainFormOnTaskbar := True;

This line is automatically added to new projects. 

For further information, see http://www.microsoft.com/windows/products/windowsvista/features/experiences/aero.mspx. 

TApplication