高手请进，关于显示器分辨率的改变问题

Question

我用下面这个程序可以将显示器分辨率改变，但是：当我由800*600改到1024*768的时候，任务栏不再屏幕下面了，网上错了1/3。不知道该怎么改。
procedure setscreen(newwidth, newheight, newfrquency:integer);
var
  devmode:Tdevicemode;
begin
  OldWidth:=GetSystemMetrics(SM_CXSCREEN);
  OldHeight:=GetSystemMetrics(SM_CYSCREEN);
  if (oldwidth<>newwidth) and (oldheight<>newheight) then
  begin
  DevMode.dmSize:=sizeof(TDeviceMode);
  EnumDisplaySettings(nil, DWORD(-1), DevMode);
  DevMode.dmFields:=DM_PELSWIDTH or DM_PELSHEIGHT or DM_DISPLAYFREQUENCY;
  DevMode.dmPelsWidth:=NewWidth;
  DevMode.dmPelsHeight:=NewHeight;
  OldFreq:= DevMode.dmDisplayFrequency;
  DevMode.dmDisplayFrequency:=newfrquency;
  ChangeDisplaySettings(DevMode,0);

Answer 1

function TForm1.DynamicResolution(X, Y: word): BOOL;
var
  lpDevMode: TDeviceMode;
begin
  Result := EnumDisplaySettings(nil, 0, lpDevMode);
  if Result then
  begin
    lpDevMode.dmFields := DM_PELSWIDTH Or DM_PELSHEIGHT;
    lpDevMode.dmPelsWidth := X;
    lpDevMode.dmPelsHeight := Y;
    Result := ChangeDisplaySettings(lpDevMode, 0) = DISP_CHANGE_SUCCESSFUL;
  end
end;procedure TForm1.Button1Click(Sender: TObject);
begin
  getfbl;
  if s = Button1.caption then
    ShowMessage('Now is 640*480')
  else
    if DynamicResolution(640, 480) then
      ShowMessage('Now is 640*480');
end;procedure TForm1.Button2Click(Sender: TObject);
begin
  getfbl;
  if s = Button2.Caption then
    ShowMessage('Now is 800*600')
  else
    if DynamicResolution(800, 600) then
      showmessage('Now is 800 * 600')
end;
procedure TForm1.Button3Click(Sender: TObject);
begin
  getfbl;
  if s = button3.caption then
    showmessage('Now is 1024*768')
  else
    if DynamicResolution(1024, 768) then
      showmessage('Now is 1024*768');
end;procedure TForm1.getfbl;
var
  x, y:longint;
begin
  x := GetSystemMetrics(SM_CXSCREEN);
  y := GetSystemMetrics(SM_CYSCREEN);
  s := IntToStr(x)+ '*' + IntToStr(y);
end;