Getting [127.0.0.1] back from name resolution?

I have a somewhat strange networking problem / phenomenon:

I am trying to use a desktop machine (running XP) attached to an
ethernet as a "Bluetooth basestation" for a second system (a laptop
running Vista), i.e. I have declared the XP machine's Ethernet as a
shared connection and I am connecting the laptop via BT networking to
the desktop machine. The laptop is configured to use the desktop as its
gateway and DNS server. The goal is to be able to access some shares on
the desktop machine as well as being able to access the internet via
this BT "bridge".

While accessing the internet works fine, acessing the other machine's
shares for some strange reason very often does NOT work (it works
*sometimes* but only in maybe 25%). After some investigation I believe I
have found the reason and it appears to have to do with name resolution.
I noticed out, that in situations when I can NOT access the shares then
when I do a "ping <desktop-machine>" I am getting:
-----------------
Pinging <desktopmachine> at [127.0.0.1] with 32 bytes of data:
Reply from 127.0.0.1: bytes=32 time<1ms ...
....
-----------------

So the ping works (and it's fast ;-) ) but that's obviously NOT what I
meant.[127.0.0.1] is localhost and obviously not the desktop machine!!!
It almost appears as if the laptop requests the name of
<desktop-machine> from its "name server" and the desktop answers with
"yes, that's myself!" and returns [localhost] as its address, not its
actual IP address that it has on the BT network (which would be
[192.168.0.1]) nor the one on the ethernet.

If I ping [192.168.0.1] explicitly that works as well (a bit slower of
course, about 35ms), so it is apparently NOT the connectivity that's the
issue here but the name resolution, that's unrailed here for some
reason!

How can I configure the desktop machine such that is passes out its real
network address and NOT [localhost]???

Michael