SQL server 2000 can't connect to another one ??

Hi,

I have SQL Server 2000 installed on a computer running Windows 2000 Advanced
Server.
I'm using enterprise Manager from the Windows 2000 server to try to connect
to another SQL Server 2000 installed on Windows 2003 server .
Whenever I tried to make the connection , I get the following error:
"SQL Server does not exist or access denied"

I read a lot of issues coming up when SQL 2000 is installed on windows 2003
server but i can't seem to find the solution.

All the latest patches and services packs are installed on both servers and
SQL servers.

I checked the client network utility to make sure TCP/IP and Named pipes are
enabled on both servers . Everything is identical . No aliases exists either.

I'm able to connect from my Windows XP workstation using Enterprise Manager
to the SQL Server running in Windows 2003 server , but NOT from the Windows
2000 server.

Also, i search the Microsoft Knowledge Base and I tried a lot of the
suggestions but nothing so far work.

Anyone knows what is happening here ?
Any suggestion ?

Thanks,
Hang