PostgreSQL Installation Question

I am trying to create an installer that will run PostgreSQL as a service
onto a Windows machine( 2000 or Server 2003).
The problem that I am having is that I need to have the database be
initialized by a restricted windows user. However, I do not want to demand
that the user log out and then log back in again as this restricted user.
Also, I am unable to utilize the 'runas' functionality from an installer due
to the inability to pipe it a password. Finally, I attempted using the
SU.exe functionality presented by the Windows Resource Tool Kit but found
out that it required too much alteration to the user group permissions which
I would not be able to accomplish from my installer.

Are there any suggestions for solving this problem? Any response is much
appreciated.