What motherboard and network card are you using? It could possibly be a bad driver. Try to get the latest drivers for you network card, then boot into safe mode (reboot, hit F8 real quick before the WinXP screen comes up, choose safe mode without networking), uninstall the old driver, install the new one, then give it a go again. Hopefully that'll do the trick (if not, at least you upgraded your NIC drivers.

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