Databse installation problem

I have tried to install postgres version 8.3.7 as follows

rm -rf /var/lib/pgsql
mkdir /var/lib/pgsql
./configure --prefix /var/lib/pgsql
gmake
su
gmake install
adduser postgres
mkdir /var/lib/pgsql/data
chown postgres /var/lib/pgsql/data
su - postgres
/usr/local/pgsql/bin/initdb -D /var/lib/pgsql/data
/usr/local/pgsql/bin/postgres -D /var/lib/pgsql/data >pgstartup.log 2>&1 &
/usr/local/pgsql/bin/createdb test
/usr/local/pgsql/bin/psql test

then i log on database to see the version
test=> select version();
                                                version
-------------------------------------------------------------------------------------------------------
 PostgreSQL 8.3.1 on i386-redhat-linux-gnu, compiled by GCC gcc (GCC) 4.3.0 20080314 (Red Hat 4.3.0-3)
(1 row)
but its showing me 8.3.1 that was my previous version.
Could anyone tell me what is the problem.

--
With Regards,
Bhushan