Problem picking up internet

I took my laptop to my grandma's house and plugged her Ethernet into my laptop. I couldn't find the connection on my laptop. So I plugged the Ethernet back up to her computer and it said that it couldn't find an internet connection. I went to the network connection page and it said that their was a cable that was disconnected. I checked all the connections and everything was secure. The same message was present. The modem also said that it was receiving signal but not sending it. It is a cable connection. I tried to run diagnostics on the modem but it wouldn't work unless it was a dial-up connection. The computer is Windows XP software. Any ideas on what I could do to get a connection?