me/xp conflict

I have 1)a laptop ME, 2)a desktop ME, 3)a laptop XP Pro,
and 4) a desktop XP Home.
Of the 24 possible combinations of these using them as
Guest or Host, 22 of them can be connected with a DCC
cable. Only the desktop ME as the host fails with the 2
XPs. The 2 XPs can communicate, back and forth, with the
laptop ME. I have gone through the Parallel Tech and the
tips and int of Carey Holzman. The 2 failed connections
are the ones I really need. Any suggestions?