WinXP Pro on a Win2000Adv Server

I have spent many weeks trying to get this to work, but for some reason I
can map drives from the XP machine to the rest of the network. None of the
other machines on the network can map any XP drives. I figure I'm missing
something fairly basic, but I can't see it. The roaming profile that is setup
on the 2000 Advanced Server is working fine on the WinNT4.0 desktop, but I
want to get rid of it and use the XP machine with that same profile. I've
spent 2 days on the Knowledge Base with no success. Any assistance would be
very much appreciated. I don't normally log onto the net from home too often
(it costs too much), so a direct email would be good if that's possible, I
can check it at school. My email addy is (E-Mail Removed)

Added Information: The WinXP Firewall is turned off, The Win2000AdvServer
is the Domain Controller, The WinNT4.0 Desktop is working fine and has been
for many years. I want to get the WinXP machine to use the existing Roaming
Profile so that I can then strip the WinNT 4.0 machine for spare parts.
Amongst the roaming profile files is the MS Outlook *.pst & *.pab files I
wish to use on the new machine. Please help, my head is almost bald from
pulling my hair out