So all other devices accept for the XP PC is working right?
Can you do a ipconfig /all from the command line in xp? What are the results?
Might do a ipconfig /release, ipconfig /flushdns then ipconfig /renew from the command line as well.
Might un-install the adapter drivers from the PC, Move the NIC to a different slot on the Motherboard, then reinstall the drivers. Do this with the LAN cable disconnected.