W2K Server/ Exchange Server 2000

I have W2K Server and Exchange server 2000 installed on one CPU. DNS not installed. AD is installed. Exchange works fine with test computer installed in test network.

Problem is when I connect to our Windows NT40 network the two will not talk.

Should I leave the w2k network as is and remove the Windows 40 network?

We are slowly bring the network up to W2K. All our files are on raid drives and backed up. The only thing on the servers drives are the OS.