OK can you try rebooting into Safe Mode (Windows XP right?), go into device manager and right-click - remove or uninstall the network card, then reboot and disable it in the PC BIOS (if possible.. sometimes Dell boards don't give you that option). Restart again and let it boot up. If that doesn't work you might need to do a Windows repair - you will need the original CD or Dell restore disk to do this. To be sure you don't lose any data you will need to back up your drive first to a USB thingy or by removing it and installing into another PC. Also check the logs under Computer Management, System Tools, Event Viewer, System log and see if there are any red X error messages relating to networking and post them here