facing problem for first time using PostgreSQL

while the postgresql-8.1.3-1 installation,for the section "install as a
service"

if i selected or checked it and press "next"...the msg ....do not hv "log on
as a service"right.........prompt out (figure1.jpg).if i press "No"
,critical error msg appear (figure2.jpg).else the msg (figure3.jpg) display
"successful granted ....right".then immedialy the error msg prompt out (
figure4.jpg). so i can only continue the installation if i uncheck the
"install as a service". finally the installation done..

but when i try to create database with "createdb batch", but no
successful... msg appear like below (figure5.jpg)
createdb: cound not connect to database postgres:cound not connect to
server: connection refused (0x0000274D/10061)