Eric, you are probably in good shape and will not lose any data.
The postgres data files can all be found under the postgres data directory.
Try running "pg_config --configure" (the old binary, assuming that it matches the MD5 checksums and is not therefore compromised); or if you have exactly the same setup on the new system, just look at where the data files are there. The data directory usually holds postgresql.conf and pg_hba.conf as well - so typing "locate pg_hba.conf" should work.
How to recover: assuming that both Postgres instances on the old and new drives are the same version and revision of the Postgres code:
make a backup of the old data directory, e.g. cp -R /old/data /root/pgbackup-data
su - postgresql (or whatever the postgres user is called on your system)
export PGDATA=/old/path/to/files
pg_ctl start (after a few lines you should see that Postgres is running)
then run psql -l to see if your databases are there.
At this point, the first thing to do is make a backup using pg_dump ; then, if that is successful, start up Postgres using the "new" file locations that reference the new drive and load your pg_dump backups.
