Is this is the same network card, you may have nothing more than a bad cable.

Have you tried other adapters?

Yes, this is the original that shipped with the PC.  It's not a PCI card but intergrated into the motherboard.

Reasons for the "Network Cable Unpligged" message:

1. The network cable really is unplugged.
2. The network cable is defective.
3. It's plugged in, but there's nothing connected to the other end.
4. It's plugged in and connected on both ends, but the device on the other end isn't turned on.
5. The cable is the wrong type. Connecting two computers directly, without a hub, switch, or router, requires a crossover cable. A regular, straight-through cable won't work.
6. The cable is connected to the uplink port on a hub, switch, or router, instead of a regular port.
7. Some hubs, switches, and routers disable the port next to the uplink port when the uplink port is in use.
8. The network card driver program isn't working right. Download and install the latest XP-compatible driver from the manufacturer's web site.
9. The network card is configured to automatically sense speed and duplex settings but isn't doing it correctly. Set those options manually, as shown here:
10. Time for a new network card.

http://www.practicallynetworked.com/sharing/troubleshoot/networkcard.htm

(Credit goes to the Microsoft.Public.WindowsXP.network_web newsgroup and Forum Regular volcano11 for developing this check list.)