Help--Network setting screw uo

I have a Compaq tower system running 98 (SE?) with a dial up modem. It was
running fine until...

I recently acquired a HP Pavillion dv6000 and ordered a wireless router so
that I can network the two computers. The router has not yet arrived.

I thought that I would do some preliminary set up and started with the
Compaq system.

I started to set up the network and I think changed a setting. In any
event, I now get an error message when I try to use Netscape Mail and I get
an error message when I try to download updates for AVG virus checker. Both
of those messages close me out of the respective programs.

How can I get things back to where I was before?

JP