There is this computer I came across in my workplace that was okay but at sometime it could not see the other computers connected to the LAN .I have checked the IP address and I think its okey.What could be the problem.

There could be many things, but the first thing that comes to my mind is, is there a Shared Folder on each of the systems that are trying to see each other? The folder also needs to have at least one file in it.

This computer is in a workgroup and should be able to see other comuters when one opens my network neighborhood but it only sees only 4 machines out of more than 40

If this computer can see four others on the network, then it should be set up properly. Assuming the other four computers can see the rest of the network of 40+ computers as well as this one, then it seems there must be a problem with the physical connections somewhere. Have you tested all the cables to make sure they're good? With that many computers, there must be some routers, switches, and/or hubs; one of those could be bad. Other than that... :rolleyes: I dunno.

Check those things and post the results. If that doesn't fix it, maybe someone else will have some ideas.

I'm with dlh6213 on this one, bad cable would be the first thing I'd be looking at, as I've seen this exact error with a cable that was severely pinched, (had a kink in it, pulled tight!).

What OS are the machines running?

Try opening any folder and typing \\computer where "computer" is the name of the computer you want to access.