Internet explorer does not work

I have a network of nearly 200 systems in mixed mode .we have two internet connections they directly came on to server machines we have installed squid proxy to share internet connection.
My problume is in some machines(win 98) sites local as well as internet are not opening i am able to ping my gateways but unable to ping any site it says host not found. i have reinstalled the network card but nothing happnes.
Pls help me,