This is a whopper and I need to figure it out so it does not happen again. The Setup: We have around 20-30 computers running Windows XP Professional. They are connected to a patch pannel and re-directed to 4 16-port linksys switches, all brand new. They are each linked to each-other by one wire, I am very carefull not to create unneeded loops. We have a server that acts as a domain controller, dns and dhcp controller. It has an address of 1.3 for the server and 1.4 for out going. These are also connected to the switches. We have a router with DHCP turned off acting as a gateway leading to a simple Motorola modem. The router only has one connection to one port of the switch. The Problem: There is one computer a customer brought in and I will be frank, I am making this sound simple but it had us down for 2 days. We finally unplugged everything except one laptop and the Internet started working again. When we plugged in this cable it gave a connection back to this evil laptop we were fixing. The Internet would quit working instantly. What could be on a computer, that when plugged into a network, would allow full Intranet access but no Internet access?