To create an additional instance on a box that already has SQL Server 2005 installed, you will need to:
1. Run the “setup” on disk 1 of SQL Server 2005 install disks
2. One page of the install wizard prompts to use “default” instance, or create a named instance. Select create a named instance and enter the name you want to call the new instance.
3. After installation, will need to apply any service packs (ie: SQL Server 2005 Service Pack 3). Even if you have applied this service pack to existing instances, will still need to apply this for the new instance.
4. After install of the service packs, you will need to run the SQL Server Configuration Manager. This can be found in “Start”->”Microsoft SQL Server 2005″->”Configuration Tools”->”SQL Server Configuration Manager”. In this tool’s UI, expand “SQL Server 2005 Network Configuration”, then select “Protocols for xxxxx”, where xxxx is the instance name you created in step 2. You will then Enable the TCP/IP protocol.
5. Can then use SQL Server Management Studio to connect to the instance. For the server name use SERVERNAMEINSTANCENAME (ie: vejxsefw3db1510DEVTEST)
6. During this process, you may need to stop/restart the instance several times. When the instance is restarted, the SQL Server Agent service will need to be manually started.