How to retrieve lost address book from Outlook?

As you have learned the hard way, the world of computer users is divided into two groups, those who have lost data and those who are going to. I run a backup with a networked RAID system and still occasionally have problems. I am afraid that if you have reinstalled the factory state, your address book is gone for ever, but you now know to back it up. Every so often you should export the entire contents of your default pst file, or portions thereof, to somewhere safe, like a folder in My Documents, which you back up regularly anyway.

If you are feeling geeky, why not invest in a PDA which comes with software to synchronise all your Outlook data? I have two copies of all my contacts always ready to hand.

Try doing a search for "*.pst". This will search for the Outlook contact list. If you find it, you can just import it through Outlook. If it's not there, it may have been deleted.