Win2003 SQL SERVER 2000 logon issues

server| problem
1. System Structure Environment:
A static IP LAN environment.
B all database software is SQL SERVER 2000
C a SQL Server 2000 Enterprise database server operating system is either win server or Win 2003 server.
D multiple clients that need to use the database server database.
E to facilitate testing, the SQL Server 2000 Enterprise database is installed on each client computer, and the server database is connected using Query Analyzer.
2, Questions:
A, the database server uses WIN server, the Client Query Analyzer only need to enter the database server, login name, password on it.
B, when the database server uses WIN 2003 server, open Query Analyzer to connect to the server, enter the database server, login name, password connection, the following error occurred: ' Unable to connect to server XXX: server: Message 17, Level 16, status 1 [Microsoft] [ODBC SQL Server Driver] [DBNETLIB] SQL Server does not exist or access is denied '.
C, before doing B, in the client, first with the server guest or other account login, and then open Query Analyzer, enter the database server, login name, password, the connection is successful. And with IP login to the server, in Query Analyzer can only use IP login, and with the service name log on to the server, in Query Analyzer can only use the service name login. To do an IP login first, and then do a machine name login, the server's IP and machine names can be successfully logged in Query Analyzer.
3, the main reason for this result is the win 2003 server security enhancements, I would like to ask the Master, in the win 2003 server servers, what should be done to the settings, can make the client Query Analyzer in the same way as in win-server direct connection success?