Ethernet port failed to connect

Recently, after a storm my desktop computer ethernet connection to the router (SMC) and internet failed. I could not talk to the router to check the configuration. When I connect another computer to the cable, it was able to function normally. That left my desktop ethernet port being the culprit. When I checked Device Manager, it reported that the network card is enabled and working properly !
I am considering installing a wireless card or a USB wireless device to access the router.

Can anyone tell me if this is a hardware or a software(configuration) issue? How do I check this?

My computer: HP Pavilion a600n/XP Home SP2

Thanks,
Tim Hoang