Follow these steps
Win98 Desktop:-
Right click on the network neighbourhood
Click on properties
Select the TCP/IP for Dial or Ethernet depnding on your type of connection
Click on the properties button
On the ip tab enter the ip address
and the subnet mask
On the gateway tab enter the gateway
On the DNS configuration entert the primary and the secodary dns dens provided by the ISP.THis has to be entered on the snd server search order-enter both the primary and the secondary on the ADD button.
then clik on OK on all the windows
and the restart your computer
and also your modem
and you should be able to able to acces the internet