Here's the problem: I'm trying to set up the network in my friends network at her (university) house. There are 5 of them in the house. All they want is the internet to work, they dont care about file sharing and stuff like that. All of the computers are running windows XP. Two of the computers have Internet just fine. The TCP/IP was set up by DHCP in both cases. The other 3 computers for some reason can't connect with the router (8 port 3Com Office Router). I tried manually configuring the IP address and all that stuff, nothing worked. I also tried unhooking one of the computers and hooking it up with the cable of a computer that was known to work but to no avail. That tells me that the cable is not the problem. All the lights on the router are green. Any ideas here would be greatly appreciated. Let me know if I missed any essential details.

Just because the cable is good doesn't mean the port on the router is. Do the test again but plug into a known good port. If you do a ipconfig on a working machine what is the ip address? If you do the same on a nonworking station what is the ip? All nics set to dhcp? Do the lights go on the switch concerning the ethernet port connections to the non working pcs? How many dhcp addresses is the router configured for? You are dealing with either a physical issue or a configuration issue. Eliminate the physical then move on to the configuration.