I've written a guide to using the Autosave Vault in Final Cut Pro 7. From the MediaStorm blog:
Final Cut Pro’s Autosave Vault is your insurance policy against crashes, lost work and just about any other mishap. In short, it will save your bacon.
The vault works by saving an entire copy of your Final Cut Pro project file at a regular, user-determined interval.
This post will explain how to set up your Autosave Vault, copy items from a backup to your working project as well as replace your FCP file with a backup file.
Read the full post here.