All of the instances installed should show up in the Services Snap-In in the Microsoft Management Console. To get the instance names, go to Start | Run | type Services.msc and look for all entries with “Sql Server (Instance Name)”.
This will list all the sql servers installed on your network.
At a DOS prompt of an SQL server:
(Note: must be a capital L)
There are configuration options you can set to prevent a SQL Server from showing in the list. To do this…
At a DOS prompt:
In the enabled protocols list, select ‘TCP/IP’, then click properties. There is a check box for ‘Hide server’.