Network connection i assemble a new comp. with msi main board model K9MM-V via K8M800+8237R plus chipset based durable, the problem is that no very offten the network connection is disconnect. after 2 -3 days automaticaly network connection is appeared

It is difficult to find a problem that happens only every 2 or 3 days! I think the first step would be to find out if it is the computer or another part of the network. Do other computers on the network continue to work while this one fails? Can you connect it to a different network and see if it works there? Are you connecting through a router? Does the connection light (computer and router and modem) stay on when the failure occurs? Also check the modem light on the phone line side to see if it is a phone line problem. Lights off on the computer side could be a problem with the cable. Replace the network card and see if that solves the problem? Could it be a duplicate IP address? One time I saw a computer that had this exact problem. It turned out to be a duplicate MAC address. That seems impossible, but it seems a company made a whole lot of computers with a built in network card and they all had the same address. No problem when connecting through a router, but connecting directly to the modem worked okay until someone else with one of these computers using the same ISP connected.