While attempting to retrieve a list of installed databases on my PC using SQLDMO in C#, I found that the named instances of SQL never showed-up no matter what I did.  Since my PC only has two named instances of SQL server installed and no default instances, this created a problem!

As it turns-out, the Windows Firewall was blocking calls to the SQL Browser’s UDP port 1434.  If you turn-off your Windows Firewall, you should be able to retrieve all named instances of SQL Server that are installed on your PC.  I opted to un-block this port so my app would work.