Unable to connect to a production sql server 2000 database

I can not connect to the production SQL SERVER 2000 database using the
Enterprise Manager or the Query Analyzer on my work station.

I am getting the error,
"A connection could not be established to "". Reason: SQL Sserver does not
exist or access denied. ConnectionOpen(Connect(())..

This problem has occurred since the production SQL Server has moved to a
different ip address.

I have already right clicked on the icon for the production SQL Server to
try to change the registration properties. However, I do not see anything
that refers to ip addresses.

It would seem like I would use the "register SQL Server Wizard" to setup a
new connection but it does not seem to have the options I need.

Thus would you let me know what I need to do to setup this connection to the
production sql server has been changed to?

Note the following 2 items:

1. When I started at this small company, they put me at a workstation that
already had access to SQL Server already setup.
2. When I used SQL server before, I used windows authenication mode.

Thanks for your assistance.