InstallAware

This function simply returns empty variable, when the instances for sure exists. Any hints why?

Many similar posts on this topic are on this forum. Usually connection settings and security settings are the cause.

See the SQL Server 2005 Express prerequisite (in the check script) to see if the service is running.

Its name is (from memory): MSSQL$INSTANCENAME

I am not sure if your are referring to the same method in your post.