I was going to say you still need 64-bit drivers, as that edit link suggests - 64-bit drivers are often not easy to find for XP. Many legacy hardware makers never provided 64-bit drivers, and many new hardware makers don't provide any XP drivers (32 or 64-bit).
You say you cannot connect to the Internet, but in actuality, you cannot connect to your network, right? Your router is not seeing this NIC, thus will not assign an IP. Right? I wonder if you tried to install 32-bit XP instead of 64-bit if you could connect?
It's been a few years since I have done anything in XP, so even on that end, I am feeling a bit out of place.
Yeah, every time an XP system comes across my bench now, I stare at the screen wondering why it looks so foreign and "clunky" to me now. Then, once the cobwebs clear and I remember what to do, I agonize at how slow XP is. Amazing for an OS I was so happy with for so many years (I never migrated to Vista because XP with SP3 was so solid - and Vista sucked).