Cannot delete folder on win XP

Hi all,
I have small app (was written by Delphi 7) to delete a folder (include sub folder and children files).
Main code of this app is below method:

procedure TForm1.DeleteDirectory(const Name: string);
var
  F: TSearchRec;
begin
  //Delete image folder
  if FindFirst(Name + '\*', faAnyFile, F) = 0 then begin
    try
      repeat
        if (F.Attr and faDirectory <> 0) then begin
          if (F.Name <> '.') and (F.Name <> '..') then begin
            DeleteDirectory(Name + '\' + F.Name);
          end;
        end else begin
          DeleteFile(Name + '\' + F.Name);
        end;
      until FindNext(F) <> 0;
      RemoveDir(Name);
    finally
      FindClose(F);
    end;
  end;
end;

Problem:
When I run app in Window 7, selected folder (folder name is input param of method) was deleted (all children files, sub folder and main folder were deleted).
However, if i run app in window XP, all children files were deleted but folders (sub folder and main folder cannot be deleted).
I have solution for this problem, but i want to know why, why program can delete folders on window 7 but cannot delete folders on window XP?

Thanks for your support!