I saw this DHCP error recently on a customers PC, I tried updating the driver for the network card but that didn't cure it. In the end I had to replace the network card, and that fixed it.
Although I wouldn't be surprised if your winsock is still corrupted perhaps. Here's a useful link to get you started:
http://windowsxp.mvps.org/winsock.htm
The above link mentions LSP's I had not heard of this term before, but it seems to relate to additions to winsock made by third party software and drivers you might have installed, that were not installed on the machine you exported winsock from. You said you were instructed to import winsock from another computer, that's fine but means you may need to re-install some things like the driver for your network card.
DHCP is Dynamic Host Configuration Protocol, it is the protocol used for a network card to lease an IP address from a DHCP server, most DSL/ADSL routers have a DHCP server running on them. The lease is typically 24 hours but varies across devices. When the lease is half up your network card will ask The DHCP server to continue the lease, it appears from your event veiwer message that this is where things are falling over, and explains why your problem is periodic, I wouldn't be surprised if your router is configured for a 4 hour lease.
The standard ethernet network cable is Cat5 UTP (Unshielded Twisted Pair) This is usually printed olong the cable. it has four pairs of twisted wires. The jack on the end is an RJ45 connector.
If you can't repair winsock, you could try either re-installing your OS or purchasing a new Network card.