A friend has asked me to look at his machine. It is XP SP3, with 2 NIC cards.
I found that the machine had some Malware on it, which I removed with MalwareBytes.
However, the machine still will not connect to the Internet. It doesn't seem to recognize when you plug into the first network card. When you plug into the second, it appears to get a DHCP address, and says "Connected" but cannot get out to the Internet.
Occassionally, a "Generic Host Process for Win32" error pops up, saying that svchost has crashed. I am not sure that it is directly connected, but it does appear to happen shortly after trying to connect to the Internet, or trying a "Repair" on the network connection.