var
  OpenDialog: TFileOpenDialog;
  SelectedFolder: string;
.....
OpenDialog := TFileOpenDialog.Create(MainForm);
try
  OpenDialog.Options := OpenDialog.Options + [fdoPickFolders];
  if not OpenDialog.Execute then
    Abort;
  SelectedFolder := OpenDialog.FileName;
finally
  OpenDialog.Free;
end;

if SelectedFolder[ Length( SelectedFolder ) ] <> '\' then
  SelectedFolder := SelectedFolder + '\';

uses FileCtrl;
const
  SELDIRHELP = 1000;
procedure TForm1.Button1Click(Sender: TObject);
var
  Dir: string;
begin
  Dir := 'C:\Windows';
  if FileCtrl.SelectDirectory(Dir, [sdAllowCreate, sdPerformCreate, sdPrompt],SELDIRHELP) then
    Label1.Caption := Dir;
end;

function GimmeDir(var Dir: string): boolean;
var
  OpenDialog: TOpenDialog;
  OpenDir: TOpenDir;
begin
  //The standard dialog...
  OpenDialog:= TOpenDialog.Create(nil);
  //Objetc that holds the OnShow code to hide controls
  OpenDir:= TOpenDir.create;
  try
    //Conect both components...
    OpenDir.Dialog:= OpenDialog;
    OpenDialog.OnShow:= OpenDir.HideControls;
    //Configure it so only folders are shown (and file without extension!)...
    OpenDialog.FileName:= '*.';
    OpenDialog.Filter:=   '*.';
    OpenDialog.Title:=    'Chose a folder';
    //No need to check file existis!
    OpenDialog.Options:= OpenDialog.Options + [ofNoValidate];
    //Initial folder...
    OpenDialog.InitialDir:= Dir;
    //Ask user...
    if OpenDialog.Execute then begin
      Dir:= ExtractFilePath(OpenDialog.FileName);
      result:= true;
    end else begin
      result:= false;
    end;
  finally
    //Clean up...
    OpenDir.Free;
    OpenDialog.Free;
  end;
end;