ms-help://MS.MSDNQTR.2003FEB.1033/shellcc/platform/shell/programmersguide/shell_int/shell_int_programming/taskbar.htm — в msdn для taskbar

Managing Taskbar Buttons

The Shell creates a button on the taskbar whenever an application creates a window that isn't owned. To ensure that the window button is placed on the taskbar, create an unowned window with the WS_EX_APPWINDOW extended style. To prevent the window button from being placed on the taskbar, create the unowned window with the WS_EX_TOOLWINDOW extended style. As an alternative, you can create a hidden window and make this hidden window the owner of your visible window.

The Shell will remove a window's button from the taskbar only if the window's style supports visible taskbar buttons. If you want to dynamically change a window's style to one that doesn't support visible taskbar buttons, you must hide the window first (by calling ShowWindow with SW_HIDE), change the window style, and then show the window.

выше, ниже тоже интересно посмотреть эту статью.


для Ctrl-Alt-Del — возможно.
но не знаю как. (встречал, но ни разбирался, ни запоминал ссылку)