• I assumed 32 is the max limit but its 50.

    http://msdn.microsoft.com/en-us/library/ms143432(SQL.90).aspx

    50 instances on a stand-alone server for all SQL Server 2005 editions except for Workgroup Edition. Workgroup Edition supports a maximum of 16 instances.

    SQL Server 2005 supports 25 instances on a failover cluster.

    SQL DBA.