We have 4 computers set up to the network here. 2 in the same room, one next door, and one downstairs. We are using DSL and a cable that runs from the upstairs computers down to the downstairs one. The downstairs computer lost network connection in the middle of the night when no one was on it. They can't find the network or get on the internet. We tried to do network setup but the computer is only finding itself. I can send packets but it cannot receive. We know it isn't the cable or the network card. This has happened before and we bought a new cable and network card but that wasn't the problem. A friend came over and fixed it then and we don't know how. Can anyone tell me how to fix this problem because it is getting really annoying?

Have you tried unplugging the modem and router and turning off the computers? Wait a few minutes and then turning the modem on followed by the router and computers?

Have a look at see how the network IP addressing is setup on that machine. It could be that it is set to a static IP address. If others are set to DHCP they could possiblly be getting the same IP address as the static machine. This will stop the static machine from accessing the net properly.

First thing to look at is the IP address on the PC that is not connecting properly. Rum Command Prompt and type "ipconfig /all" this should tell you what the IP is and if it is using DHCP.

If you could report back your findings that would help.