public class SubWindow : NativeWindow
    {
        [DllImport("user32.dll")]
        public static extern int ShowScrollBar(IntPtr hWnd, int iBar, int bShow);

        const int SB_HORZ = 0;
        const int SB_VERT = 1;

        protected override void WndProc(ref Message m)
        {
            ShowScrollBar(m.HWnd, SB_HORZ, 0);
            base.WndProc(ref m);
        }
    }