Install PostgreSQL as part of a desktop application, but how to coop with existing installations?

Hi,

I am looking into using PostgreSQL as a database service in a desktop
application since it's one of the support local database systems by
DataObjects.net and has more features and higher limitations than SQL
server express. I prefer a database versus a traditional binary data
file, but I ran into some limitations when using either SQLite or SQL CE
3.5. (Support, file lize limitations, no batch processing support, ...)

I know that some applications (Poker Tracker 3 is the first one that
comes to my mind) install PostgreSQL during their installation process
too and setup the initial database. I sort of figured out how to do
this, but I don't know how to deal with an already existing installation
during setup. What if the user doesn't now the master server password.
As far as I understand this means I cannot continue the installation
process and create my databases.

Is there somewhere a guide to include and configure PostgreSQL as part
of a desktop application? More precisely installation and configuration
steps that clarify my question?

- Jensen