A system menu can be attached to any standard window. When an item is
 chosen, the WM_SYSCOMMAND message is sent to the window who owns the system
 menu. You can give a window a system menu by specifying the WIN_SYSMENU or
 WS_SYSMENU style in the CreateWindow() call. To invoke a system menu, use
 the ALT-SPACE key or click the mouse on the system menu.

 A system menu is just like any other menu. You can modify the system menu by
 using any of the functions above.

 WinGetSysMenu
 WinCreateSysMenu
 WinActivateSysMenu