Reinstall Network card
(Microsoft Windows XP->Driver installation)
1. Click "Start", go to "Run", type in "devmgmt.msc" and press "Enter".
2. In the Device Manager, expand "Network Adapters".
3. Right click your network card and click "Uninstall".
Then, restart your computer. If its driver has been built in Windows XP, it will be detected and installed automatically.