Sometimes, when you install a new LAN card, your system could hang. If that happens, open your machine’s cabinet and remove the LAN card. Clean the LAN card’s golden connectors as well as the PCI slot on the motherboard. Re-plug the card and make sure that the card sits properly in the slot. Now restart the system in Safe Mode and go to Start > All Programs > Accessories > System Tools > System Information > System Summary > Hardware Resources > IRQs. Check if any IRQ is conflicting with another.