Problem with cable internet LAN on laptop.?

Someone gave me a used laptop. I tried to hook it up to my cable ethernet, and it won't work with it. First it didn't recognize the connection, so I downloaded new drivers. The drivers helped it recognize that there was a connection, but then I got an error message that said the connection wasn't working because I had to renew my IP address. I followed the directions to do that (found directions online), but it's still not working with the ethernet connection. It works when I'm in a wifi hot spot, but I don't have wifi at home. The previous owner had set up 2 broadband connections -- would this affect whether it would work with my cable modem? Do laptops get attached to their first connection and then are unable to adapt to new ones? Any helpful hints? Thanks. I'm trying to keep costs down. I only paid about $100 including shipping for this laptop -- it's an XP -- and I really can't afford to take it somewhere to have it worked on. Thanks.