Since I've used Outlook pretty much for the last 9 years of my life at work (through various versions and companies I've worked), I've now come to the conclusion that the Email Address AutoComplete is quite useful. You start typing and a list of emails you've written to comes up, select the desired email and you're ready to write your email.

I've recently come across two situations with this feature. A colleague needed for the AutoComplete to be emptied so not to email to addresses he was no longer supposed to send email to and another who got a computer upgrade and wanted to continue to use this feature without having to rebuild it. So I Googled away as always and I came across this article and this KB from Microsoft. Since they're a little bit out of date they both fail to mention Vista or Windows 7 so I've figured out where the .nk2 file is!

The location for the outlook.nk2 in Vista and Windows 7 with Outlook 7 is the following:

C:\Users\username\AppData\Roaming\Microsoft\Outlook

The key difference here is that you need to go to the Roaming folder instead of the Local folder as specified in the other articles.

Hope this helps someone!