Win 98 networking

I am on a Win 2000 server network with most (100) computers running xp. A few have 98 and the one I am having trouble with is saying that it is in conflict with a machine, and it gives the Mac address of the machine. I went into the server (DHCP) and could not find the Mac address. The NIC light is solid green, does this mean anything? I can ping local host but cannot ping the server. All the TCP/IP properties seem to be configured correctly. And all cables are connected. Any suggestions? Thanks.