Well, you could override the KeyDown/KeyPress and ignore those
combinations, or handle the OnClosing event and check for what kind of
closing is performed
protected override void OnClosing(CancelEventArgs e)
{
System.Diagnostics.StackTrace O = new System.Diagnostics.StackTrace(true);
System.Diagnostics.StackFrame F = O.GetFrame(7);
if(F.GetMethod().Name == "DefWndProc")
e.Cancel = true; // user ended the application (ALT-F4, clicking the
corner X etc)
}