Found this useful article that explains Outlook's Auto-Complete feature:

http://www.outlookpower.com/issues/issue200506/00001584001.html

"If the users are losing addresses of people they recently replied to, it's because Outlook crashes or does not close properly and the changes aren't written to the NK2 file. The existing *.NK2 shouldn't be replaced by a clean *.NK2 if this happens, but new addresses you've sent mail to, or replied to won't be saved to the file. Less used addresses are replaced by new addresses when the NK2 contains 1000 addresses, but if something is corrupt, Outlook replaces the current NK2 with a new, clean one. We don't know what causes it to become corrupt, but we suspect a large number of addresses in the cache is part of the problem."

If you're anything like me, you don't like having programs you don't use start up when you open other programs. If I wanted to open it, I would open it myself or have it start up when my computer boots up. I had a tech request recently that dealt with Messenger starting up when Outlook 2002 starts. Here's how to disable that:

Open Outlook and select Tools from the menu bar
Under Tools, select Options
Select the tab named Other
Towards the bottom you'll see a section named Messenger
Uncheck the box next to "Enable Instant Messaging in Microsoft Outlook"
Click Apply
Restart Outlook

Now that little messenger icon next to your clock shouldn't pop up again when you open Outlook 2002