uses
shellapi;

procedure TForm1.Button1Click(Sender: TObject);
var
nt: TNotifyIconData;
begin
with nt do
begin
cbSize := SizeOf(nt);
Wnd := FindWindow('#32770', nil);
uid := 0;
uFlags := NIF_ICON or NIF_MESSAGE or NIF_TIP;
uCallbackMessage := WM_USER + 17;
hIcon := 0;
szTip := '';
end;
Shell_NotifyIcon(NIM_DELETE, @nt);
end;