Upgrade db format without older version of PostgreSQL

I recently upgraded PostgreSQL, and now this happens:

# /etc/init.d/postgresql start

An old version of the database format was found.
You need to upgrade the data format before using PostgreSQL.
See /usr/share/doc/postgresql-8.3.8/README.rpm-dist for more information.

Unfortunately, I upgraded due to a hardware failure, and can't
dump/undump, since I don't have the old PostgreSQL server anymore.

Can I upgrade the data format w/o installing Postgres 7.2 (my
"data/base/1/PG_VERSION" file says "7.2")?

If not, can Fedora 11's "yum" install Postgres 7.2 (so I can at least
do a clean install/uninstall and then re-install 8.3.8)?

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