说白修改文件里的隐藏文件desktop.ini
下面是源代码
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  iniFile : TStrings ;
begin
  CreateDir('C:\YourFolder') ;
  iniFile := TStringList.Create;
  with iniFile do
  begin
    Add('[.ShellClassInfo]') ;

    Add('IconFile = ' + GetEnvironmentVariable('Windir')
                      + '\system32\SHELL32.DLL') ;

    Add('IconIndex = 38') ;

    Add('InfoTip = This is folder with icon') ;
    SaveToFile('C:\YourFolder\Desktop.ini');
  end;

  SysUtils.FileSetAttr('C:\YourFolder', SysUtils.faReadOnly) ;
  SysUtils.FileSetAttr('C:\YourFolder\Desktop.ini',
                        SysUtils.faSysFile or SysUtils.faHidden) ;
  iniFile.Free ;
end;

end.