Network cable is unplugged

I have two pc’s connected to each other and the link lites are on, on both the pc’s yet i continuosly get that the network cable is unplugged on the one pc. I have made sure that they each have seperate ip addresses.On the problem pc i right click on the local area connection and select disable, once that is done i do the same only i select enable, after a couple of seconds it tells me there was a connection error and go’s back to network cable unplugged.Both computers are running XP Pro HELP PLEASE!!