Router does not recognize wired LAN computer

I have a D-Link DIR 655 router. This computer, a network drive, (both wired connections) and multiple wireless devices (iPad, iPhone, Blackberry, Motorola Atrix) are recognized by the network. However, another computer that has always been connected via wired LAN is no longer being recognized. The computer has full internet access, but the networks does not see it, and so I cannot access the network drive to back up this computer. Any suggestions? I would assume the cable is fine since I can access the internet. I set filter in the router to accept the IP address but that did not solve the problem.

Computer configuration: XP Professional SP3; connected through ATI Radeon HD 4800 (tried both ports, same results).

Thanks in advance!

 

Are you sure that it is not the Computer not recognizing the router. Have you tried a different nic in the computer, or cable?