Geoff Hart:
One really important tip for all Mac users: when you do your regular backups, make sure you open the System folder and make a copy of the Preferences folder, plus any other related folders (e.g., MS Preferences Panels if you use Word, Eudora Settings in the Eudora folder if you use Eudora). If your preference file gets corrupted, simply replace it with the backup copy. Saves a whole world of hurting when the inevitable corruptions occur.