Help with starting portable version of postgresql

Hi,

I downloaded the portable version of Postegresql from
http://greg.webhop.net/postgresql_portable

It works but the problem is that to start the server you must load it from
the gui. Instead since I want to start the server from my app, I need to
understand how to load it manually. I tried starting postgres.exe but it's
saying:
Execution of PostgreSQL by a user with administrative permissions is not
permitted.
The server must be started under an unprivileged user ID to prevent
possible system security compromises. See the documentation for
more information on how to properly start the server.

That0s strange, because the gui instead is able to load it so I'de like to
know how can I do the same thing (and I can't find the source code of the
ui).

Thanks a lot in advance,

--
Marco Di Antonio