Can't share drives or access Exchange

I've had a dial-up connection from XP/Home to NT4 server for a while now
that I use to access shared drives on the NT4 system and to access
MS-Exchange via Outlook. I recently installed a USB network cable so I could
connect my laptop to the XP/Home system and that went in Ok.

Now, I can't access any of the shared drives on the NT4 system or
synchronise my diary via Outlook/Exchange.

I've tried dialling up to the NT4 server and that works fine. Once connected
and logged on, I can ping the addresses that I know about (FTP and HTTP
services). However, when I try to synchronise my diary or try to access a
shared resource, I get no response from the NT4 system.

My understanding is that shared resources and Outlook/Exchange use NWLink
IPX/SPX for their communications, so I guess that's where the problem lies.
However, I know next to nothing about networking so don't know how to go
about properly diagnosing the problem, let along fixing it.

I've uninstalled the USB network cable, but that did nothing for me. I've
also tried uninstalling NWLink (which causes the machine to hang) and then
re-installing it (after restarting the machine), but that seems to make no
difference at all. My guess is that it's something to do with binding NWLink
to the dialup adapter, but I can't see how you do that in XP/Home.

Any suggestions as to what I can do to sort this out please?

Thanks
Steve Barnett