Problem starting postgresql !!

Hi,

I had postgresql 7.3 rpm installed on redhat 9 platform. i removed it
and downloaded and installed following rpm's from ur ftp site:-

[root@reporter postgresql-7.4]# rpm -qa |grep postgre
postgresql-debuginfo-7.4-0.5PGDG
postgresql-libs-7.4-0.5PGDG
postgresql-contrib-7.4-0.5PGDG
postgresql-devel-7.4-0.5PGDG
postgresql-test-7.4-0.5PGDG
postgresql-7.4-0.5PGDG
postgresql-server-7.4-0.5PGDG

now when i try to start postgresql, i am getting :-

[root@reporter init.d]# ./postgresql start

An old version of the database format was found.\nYou need to upgrade
the data format before using PostgreSQL.\nSee
/usr/share/doc/postgresql-7.4/README.rpm-dist for more information.

could u please let me know, how to get rid of this problem.

Regards
Rahul D.