Unless you're engaged in illegal activity such as downloading music or movies from p2p networks or something similar I wouldn't worry about your IP address. However, I'm no conspiracy theorist, but the FBI does keeps tabs on internet traffic. Even as far back as 1997 when they deployed the "carnivore software". Also, if I remember right, Intel on their Pentium 3 chips, wrote in a unique I.D. number for each chip that was sent along with your internet traffic. So even if a person had gotten rid of that computer it could still be traced back to them with the IP address and the Pentium chip ID.