I work for a telecommunication firm that installs DSL, VOIP, wireless LAN, etc. Basically, you want there to be at least 50 ft. between a computer and the hub. That means at least 100 ft of cable from one computer to the other. The reason for this is resonance. A hub acts as an amplifier and repeater. Resonance occurs when a packet is sent so fast that it bounces back to the original sender, thus causing a collision. Switches can't even prevent this kind of collision. Also, when running cable, make sure you don't use any sharp 90 degree turns, this will cause the cable to kink and can also cause you to lower the overall speed of the cable and cause collisions. Free run cable. I have seen some installs where the people actually stapled the cables to the framing in a building. This not only pinches the cable, but also makes it a bitch when you have to pull new cable. A fishtape would be a good investment if you're using conduit, but could run you about $250 for a good fiberglass one. A cheaper way to get pull strings for cable is to get a vacuum cleaner and you can pull twine through conduit by applying the vaccum to the other end of the conduit. If you know anyone that works for a computer firm you can see if they could come over with a Microtest Penta Scanner and check the impedance, pentas, and wiremap of your terminated cable. This makes sure that the cable will actually run at 100 Mbps, you have no crosstalk, and that you have the RJ45 mod plug terminated correctly. Also, make sure that no run between two computers is more than 328 feet (100m). You can run Cat 5 over 328 ft., but you get signal degradation the further you go.