service postgresql start Fails, Can't su

Hello,

[root@server root]# service postgresql start
Starting postgresql service: Password:
su: incorrect password
                                                            [FAILED]

I've tried this as the postgres user as well and get:

[root@server root]# su postgres
Password:
bash-2.05a$ cd
bash-2.05a$ service postgresql start
postgresql: unrecognized service

I'm wondering if this would have worked if I had not as root done:

[root@server root]# passwd postgres

to set the password for that user. But then I couldn't become that user..?

I'm wondering if this is a permissions thing? Where is it trying to su
from (the /etc/init.d/postgres file obviously, but er - from what user?
from root to whom?)? Why doesn't it know the password? Can I set it in
the /etc/init.d/postgres or somewhere else?

More info: PostgreSQL RPM was installed on my machine (a user mode Linux
virtual machine) when I got it. It's a Red Hat 7.3 and I believe
Postgres is 7.2. Should I uninstall, delete everything and start fresh?

Sorry if this is a duplicate post. I've Googled and surfed this list for
about three hours now trying to find this so I'm giving up and posting :-/

TIA,
Phillip