Explorer won’t connect to Internet.

In July we lost 7 machines to virus attacks.
We are now about finished rebuilding the system from scratch.

However we have a curious problem with two (2) of them, we cannot get Explorer to connect to Internet. (NT4.0 & SP6a).

Following Items have been double checked, and are O.K.:
All machines can talk to each other on our internal net work, network neighborhood and server manager SEE’s all machines.
IP# correct on each.
SubNet Mask correct on each.
Gateway IP# correct on each.

The two machines are DNS servers, so we did not load IIS4 onto those 2 computers to make them less likely to get another virus. Which should not effect Explorer.

Any Ideas Guys.?

Regards
George