Look at the IRQ list, and see if the NIC is having an IRQ by itself, or if it is sharing with a friendly device (USB is IRQ wise friendly, Video is bad).
Click on Control Panel /System and remove the current NIC Drivers.
Switch off the computer, take out the NIC. Reboot.
Look again at the Control Panel /System Properties, and make sure that there is no Ghost installation related to Network Hardware, if there is remove it.
Switch off again. If the NIC had a good IRQ assignment put it back in the same slot, otherwise insert it in a different slot (do not use the slot next to the AGP Video Card).
The computer will detect the NIC, and hopefully will let configure every thing correctly.
If it does not load correctly get a new NIC ( many for $5)
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If you have A Cable/DSL Router would you please post the Port Mapping Menus Names?
See here:
http://forums.anandtech.com/messageview.cfm?catid=36&threadid=1048003