안녕하세요?
배치파일은 아니고 원하시는 기능의 함수입니다. path의 하위폴더에 있는 파일까지 삭제해 줍니다.

procedure ClearFiles( Path, SearchName: String );
var
   Directory: string;
   FileInfo : TSearchRec;
   Found : integer;
begin
    Directory:= Path;
    if Path[Length(Path)] <> '' then Directory := Path + '';

    Found := FindFirst(Directory + SearchName, faAnyFile, FileInfo);

    while Found = 0 do
    begin
          if (FileInfo.Attr <> faDirectory) and (FileInfo.Name[1] <> '.') then
              if FileInfo.FindData.cAlternateFileName <> '' then
                  DeleteFile(Directory + FileInfo.FindData.cAlternateFileName)
              else
                  DeleteFile(Directory + FileInfo.FindData.cFileName);
          Application.ProcessMessages;
          Found := FindNext(FileInfo);
    end;
    FindClose(FileInfo);

    if FindFirst(Directory + '*.*', faDirectory, FileInfo) = 0 then
    begin
        repeat
            if ((FileInfo.Attr and faDirectory) = faDirectory) and (FileInfo.Name[1]<>'.') then
            begin
               ClearFiles(Directory+FileInfo.Name+'', SearchName); // 재귀호출
            end;
            Application.ProcessMessages;
        until (FindNext(FileInfo) <> 0);
    end;

   FindClose(FileInfo);
end;

사용법
ClearFiles('c:temp', '*.txt');