See comment #0 :
"... it dosn't work for the one on sda2 (~ 10 seconds after WinXP boot screen I got a blue-screen). ..."

Currently, both Windows partitions are listed in the GRUB menu, but selecting the 2nd entry actually ends up in booting the 1st, which is a error to me.

have you looked at gptsync? create a gpt partition, and use gptsync to produce the order of mbr-entries you want, then use parttool to disable gpt so windows-xp-32bit actually boots...

I changed the sources to allow for grub to function nicely if gpt and mbr modules both are loaded and boot partition is accessible only through gpt. sadly for now you're limited to 3 partitions visible in mbr. as extended partitions overlap with their children, you cannot tell gptsync to create such a parent-partition...

Pooh, how often should I explain, that there is nothing to fix in boot.ini?

Here it is. What would you think to repair here?

[boot loader]
timeout=5
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

Please forget, what I have written for grub.cfg. I wasn't aware, that partitions normally are determined by their UUID, so the assignment should work even if partitions are swapped.

So I suggest to extend the os-prober script similar like the following:
(should be controlled by a new etc/default/grub entry)

if [ x"${swapped_part_1}" = xy && x"${swapped_part_2}" = xy ]; then
  parttool $swapped_part_1 swap-order $swapped_part_2
fi
set swapped_part_1=
set swapped_part_2=
save_env swapped_part_1
save_env swapped_part_2

menuentry 'Windows XP on sda1' {
  ...
}

menuentry 'Windows XP OLD on sda3' {
  ...
  set swapped_part_1='hd0,msdos1'
  set swapped_part_2=${root}
  parttool $swapped_part_1 swap-order $swapped_part_2
  save_env swapped_part_1
  save_env swapped_part_2
  chainloader +1
}


==========================================================================
A first draft, of what should be added to grub-core/parttool/msdospart.c :
(I do not have any environment to build GRUB, so hopefully others have)
==========================================================================
<code>
static struct grub_parttool_argdesc grub_pcpart_swapargs[] =
{
  {"swap-order", N_("Swap the order in partition table"), GRUB_PARTTOOL_ARG_VAL},
  {0, 0, 0}
};

static grub_err_t grub_pcpart_swap (const grub_device_t dev1,
    const struct grub_parttool_args *args)
{
  grub_device_t dev2 = parse (args[0]); // TODO: replace parse() by valid code
  grub_partition_t part1, part2;
  int index1, index2;
  struct grub_msdos_partition_mbr mbr;
  struct grub_msdos_partition_entry entry;

  part1 = dev1->disk->partition;
  part2 = dev2->disk->partition;
  index1 = part1->index;
  index2 = part2->index;

  if (dev1->disk != dev2->disk)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("partitions must be on same disk"));
  if (index1 >= 4 || index2 >= 4)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("logical partition not allowed"));

  dev1->disk->partition = part1->parent;

  /* Read the MBR.  */
  if (grub_disk_read (dev1->disk, 0, 0, sizeof (mbr), &mbr))
  {
    dev1->disk->partition = part1;
    return grub_errno;
  }

  entry = mbr.entries[index1];
  mbr.entries[index1] = mbr.entries[index2];
  mbr.entries[index2] = entry;
  grub_printf_ (N_("Partitions %d, %d are swapped now. \n"), index1, index2);

   /* Write the MBR.  */
  grub_disk_write (dev1->disk, 0, 0, sizeof (mbr), &mbr);

  dev1->disk->partition = part1;

  return GRUB_ERR_NONE;
}
</code>