Installing SQL 2005 and SQL 2000 on the same box - what you should know?

Many customers have asked me if they can install SQL 2000 and SQL 2005 on the same box, side by side.

The answer to this is YES.

You can install SQL 2000, SQL 7.0 and SQL 2005 on the same box. However, there are certain special considerations that you should be aware off.

Co-existence of multiple versions of SQL server

First, refer to this comparison sheet published by Microsoft at the MSDN website.

This sheet can be used as a handy reference to decide if your planned configuration is supported or not.

What next?

If you already have SQL 2000 installed, then you have to make sure that it is atleast SP3 and above before you attempt to install SQL 2005.

This is very important and critical because instances of SQL 2000 prior to SP3 don’t relinquish port 1434 when SQL Browser Service starts.

Since SQL 2000 is already running on the machine, SQL listener service is listening on UDP port 1434. When you install SQL 2005, it installs SQL Browser service and tries to start it. While starting, SQL Browser service will wait for 5 seconds for SQL 2000 to relinquish port 1434. If it doesn’t, then Browser service will not start.

If SQL 2000 is below SP3, then you have to stop SQL 2000 before you can install SQL 2005.

In case you are building a new machine and have to install SQL 2000 and SQL 2005, install SQL 2000 first and then move to SP3 or above. Then install SQL 2005.

UPDATE 09/28/06

I blogged more about it here.