unable to add an DNS address

We are unable to add a DNS address on a Dell Inspirion 7500, using a 3com FE575c lan cardbus fast ethernet adapter. Client runs Win98 2nd Ed.

What happens is that we go to Net Neighborhood, Network, TCP/IP Properties, DNS Configuration, we can enable DNS and add the computer name, however we are unable to add any DNS addresses, that field stays grayed out.

We have removed the NIC and all network properties, reinstalled, updated the NIC driver and it makes no difference.

Are you lookingin the wrong area to solve this problem? Thanks for your help