After using Windows Easy Transfer to migrate my data, I noticed that my
contacts are missing when I click the To, Cc, or Bcc buttons.

I can see the contacts when I click on the Contacts section button in
Outlook 2007.

These articles seem to have helped to a point:

Outlook 2007 in Vista Does Not Display Contacts in To: Box
http://groups.google.nl/group/micros...51629e79796a6d

Contact information does not appear in the address book in Outlook
http://support.microsoft.com/default...Product=ol2002

Contacts are missing when I click the To, Cc, or Bcc buttons
http://office.microsoft.com/en-us/ou...194281033.aspx

Because "Show this folder as an e-mail Address Book" was grayed out, I
followed the steps under "Reset Outlook Address Book settings".

In step 2, under "Name", "Outlook Address Book" appears so I followed that
part of the instructions.

Step 4 of this fork says "Under Show this address list first, click
Contacts."

Unfortunately I cannot do this because the drop-down for "Show this address
list first" is not populated.

Any ideas on how I can populate the drop-down with the "Contacts" option so
that I may select it?