Restoring a postgres8.3 backup with postgres8.4
PostgreSQL uses various formats for backups. What's the format of yours?

pg_restore is only needed for backups using one of the archive file formats. The default format of backups produced with pg_dump is an SQL script that you can restore via psql:

psql dbname &lt; /path/to/backup


Start by reading the chapter "Backup and Restore" in the manual.