Windows Installation Problem

I'm not sure if I've violated some rule or the installation is just not
working the way I'm thinking it should work.

This is a Windows XP Professional Service Pack 2 install. Yes, I know
it sucks but until I get my app rewritten in Qt it will have to do and
even after that point I will still need this to work.

First I install 8.3.1 using this command line:
MSI (c) (F0:1C) [22:53:29:468]: Command Line: INTERNALLAUNCH=1
DOSERVICE=1 DOINITDB=1 SERVICEDOMAIN=CLAUDIAS-IGOR
SERVICEACCOUNT=pg$horseshow SERVICEPASSWORD=**********
CREATESERVICEUSER=1 SERVICENAME=pg$HORSESHOWTIME_8.3
SUPERUSER=pg$SuperUser SUPERPASSWORD=********** PERMITREMOTE=1
ADDLOCAL=server,psql,pgadmin
CURRENTDIRECTORY=C:\DOCUME~1\STEFAN~1\LOCALS~1\Temp\is-PSU3E.tmp
CLIENTUILEVEL=1 CLIENTPROCESSID=3824

The install works great and my service is named pg$HORSESHOWTIME_8.3,
the super user is pg$SuperUser and the superpassword is functional
allowing me to login via pgAdmin3.

Next I do (after a reboot because the service name, service user, super
user, and super password are not known until after the reboot) an
install of version 8.3.3 using the following command line:

MSI (c) (D8:9C) [23:03:06:843]: Command Line: REINSTALLMODE=vamus
REINSTALL=ALL
CURRENTDIRECTORY=C:\DOCUME~1\STEFAN~1\LOCALS~1\Temp\is-NDO44.tmp
CLIENTUILEVEL=1 CLIENTPROCESSID=3544

The second install blows out with the message that Service 'PostgreSQL
Database Server 8.3' (pgsql-8.3) could not be installed. Verify that
you have sufficient privileges to install system services.

Clearly it's trying to install the version upgrade using the default
service name rather than the service name I've specified and this same
error seems to perpetuate itself through all the possible install
parameters that are not default parameters.

Is there a piece I've missed or is this incorrect installation behavior?

Thank you for any light that you can shed on my problem.
---
Stefan Berglund