Silent start of Postgres in XP

I need to start Postgres 8.1 database in XP without any user intervention
even when Postgres is not installed.

I have implemented this for Apache2 by running the following commands:

Apache.exe  -k stop
Apache.exe  -k uninstall
Apache.exe  -k install
Apache.exe  -k start
@rem if user has no privileges to install service, start Apache as
application:
Apache.exe

This causes Apache to run under SYSTEM account .

Trying to use same approach with Postgres fails. Postgres requires special
user account and is not capable to create this account without user
intervention.

How to force Postgres to install itself as service running under SYSTEM or
under LOCAL SERVICE  account?

Andrus.