Well..., yeah..., of course, I realize it's not push a button and magic
happens, I figured if the OP was interested, THEN I would provide more
details, wanted to keep it short and sweet until then.

But yes you will need to place DOS before XP (because DOS must load within
the first 2GB and is limited to FAT/FAT16 and 2GB max size).  But that's a
trivial matter, you can use just about any partition manager to reduce the
size of the XP partition (assuming it's consuming all of the HD), and
install MS-DOS in a 2GB max FAT partition at the head of the drive.  Now use
a boot manager that that hides each OS from the other, and you're done.  No
need to reinstall XP, none at all.  It's just a simple repositioning of the
OS partitions and using the boot manager to hide them (which is always the
case), no big deal.

OTOH, if you rely on the Windows boot loader, which is a piece of crap, then
yeah, you have some problems.  It FORCES you to reinstall XP, which is why
many of us avoid it like the plague.

JMTC

Jim