Ok, I have asked this problem to every one that I work with and have come across that works in the tech industry. No one can seem to figure it out. For about the past 3 years my computer NIC has had to be set at 10Mb half duplex to maintain a conection, anything above that and it will not conect. If it is set to auto it constantly conects and disconects. I have replaced the cables and the NIC several times. None of the other computers on the network had this problem till I built a new computer and it does the same thing. I have replaced the NIC, cabling, power supply and ran a dedicated power circuit from the breaker box and none of it seems to make any diference. My router/switch is a linksys BEFSX41, the 2 computers in question are in the same room as the router/switch. All of the other computers in the house have no problem, even my laptop has no problem when it is in the room with the others. When ever I am transfering files between computers and one of them is one of the computers in question here the nic tops out at about 25% of the 10Mb conection and the graph looks like a bad saw blade. Larger files are virtualy impossible to transfer because it looses conection before they complete.