Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

procedure GetSubDirs(const sRootDir: string; slt: TStrings);
 var
   srSearch: TSearchRec;
   sSearchPath: string;
   sltSub: TStrings;
   i: Integer;
 begin
   sltSub := TStringList.Create;
   slt.BeginUpdate;
   try
     sSearchPath := AddDirSeparator(sRootDir);
     if FindFirst(sSearchPath + '*', faDirectory, srSearch) = 0 then
       repeat
         if ((srSearch.Attr and faDirectory) = faDirectory) and
           (srSearch.Name <> '.') and
           (srSearch.Name <> '..') then
         begin
           slt.Add(sSearchPath + srSearch.Name);
           sltSub.Add(sSearchPath + srSearch.Name);
         end;
       until (FindNext(srSearch) <> 0);

     FindClose(srSearch);

     for i := 0 to sltSub.Count - 1 do
       GetSubDirs(sltSub.Strings[i], slt);
   finally
     slt.EndUpdate;
     FreeAndNil(sltSub);
   end;
 end;