Are you installing any other Office 2007 apps? If so, try opening one
of those. Hopefully you'll get the dialog, fill in the info, and then
Office is happy and won't prompt you when you're working in Outlook.

There is a recent hotfix Microsoft issued on 3/10 that I think causes
this. If you search this forum, you should be able to find the KB
number and instructions on removing the patch, if need be.

Let us know if this helps; I hope it does.