At first glance this may same a duplicate of Installing both SQL Server 2000 and SQL Server 2008 on the same machine, but it is not.
I have SQL Server 2000 and SQL Server 2008 R2 installed on the same machine and working fine.
My problem lies with connecting to the 2008 R2 server from a remote machine. My connectivity needs to be TCP. The legacy installation or SQL 2000 uses the default port of 1433. The named instance is by default configured to use 'Shared Memory' and is working fine. When I configured the 2008 R2 server to use 1433 (I did not think that thru) the service refused to start becasue 1433 was already in use by the legacy SQL 2000 default instance. Doh!
What I want to do is have both servers available simultaneously via TCP. both servers need not be on the same port, put if I cannot run them on the same port, then how do I configure the clients?
Is there not some kind of proxy available that can monitor the 1433 port and pass the request thru to the correct SQL instance by name? Is this capability built into SQL server already?