//函数
function SetScreen(x,y: Word): Boolean;
var
DevMode: TDeviceMode;
begin
  Result := EnumDisplaySettings(nil, 0, DevMode);
  if Result then
    begin
      DevMode.dmFields := DM_PELSWIDTH or DM_PELSHEIGHT;
      DevMode.dmPelsWidth := x;
      DevMode.dmPelsHeight := y;
      Result := ChangeDisplaySettings(DevMode, 0) = DISP_CHANGE_SUCCESSFUL;
    end;
end;
//测试
procedure TForm1.btn1Click(Sender: TObject);
begin
  SetScreen(1024, 768);
end;