In Microsoft Outlook, I find the AutoComplete function to be quicker and more useful than the address book.
When sending emails, I usually start typing the first few characters of the email address and Outlook magically figures out who I want to send it to, based on emails I've composed in the past. The problem is, every time I install Outlook on a new computer, I lose the AutoComplete and have to start from scratch.
Well, it turns out there's a simple way to migrate your AutoComplete list from computer to computer. There is a file with a .nk2 extension that stores the AutoComplete information. It resides in the C:\Documents and Settings\{user name}\Application Data\Microsoft\Outlook folder. (You need to replace {user name} with the name of the user that's logged in. If you copy this file to the new computer, all your AutoComplete information will work on the new install. The file is basically a list of email addresses that you've typed in the past, and there is only one file involved. So it's a pretty simple procedure.
It's also easy to backup. If you do regular backups of important files (and you should), then just look for the .n2k file and back it up. This will work even if Outlook is open. Another interesting thing is that a company called NirSoft has a free utility that allows you to view and do some light editing on your AutoComplete file.
With this utility you can export your AutoComplete emails to a text file or html file. At the very least it's interesting just to see what's in there. The other good thing about NirSoft NK2View is that it's a very lightweight application. You don't need to install anything. Just download it, unzip it into a folder and run the executable. For viewing and exporting your AutoComplete emails, I highly recommend it.