Fixing "old version was found" error

I just upgraded a machine to Fedora Core 3 and now on startup pgsql gives
me the message "An old version of the database format was found" and
refuses to start.

I'm not entirely sure how to fix this (everything I've read says I
should've taken some steps before the upgrade) but since the only database
on this machine was a sample one, I don't care if it's lost. Are there
files
I can simply delete to make pgsql happy -- so we can actually start using
it?

Thanks.

Gordon