Connecting SQL server 2000 over LAN

I am using Windows XP in both client and server. whenever i try to connect client to server, the error pop up saying "sql server does not exist or access denied. connectionopen (connect())" i used switched between computers, firewall off on both sides, no antivirus or other thing installed, used windows authentication, sa user and also create another user but still same error.
When i gave server name with instant name, Server name show up there but it does not connnect please help what i am missing or share link which can help me(only sql 2000)

How are you trying to connect?

Can you PING the server from your Client PC?

There used to be a utility called something like SQLPING and/or ODBCPing which I found handy back-in-the-days-of-SQL2000