Share Contacts between Outlook and Outlook Express

Im not sure why anyone would use Outlook Express anymore – however, n certain configurations, Microsoft Outlook can expose data in the Contacts folder to the Windows Address Book (WAB) that Outlook Express users. In effect, this means that Outlook and Outlook Express are sharing the contacts. Creating a new contact in the WAB actually creates a new contact in the Outlook Contacts folder.

Note that if you turn on sharing between Outlook and OE, any data previously entered in the Outlook Express address book will not be visible until you turn off sharing. You must choose whether you want to see Outlook contacts or the original OE address book. You can’t have both.

Slipstick systems has a webpage explaining how to share the info:

Officially, Outlook 2002 and Outlook 2000 in Corporate/Workgroup mode do not support sharing of its contact data with Outlook Express, but there is a registry hack that works, at least with some versions of Outlook Express. Follow these steps:
Make a backup of your Windows registry.
Open the Registry Editor (regedit.exe or regedt32.exe).
Go to this registry key:

HKEY_CURRENT_USERSoftwareMicrosoftWABWAB4

Add a new DWORD named UseOutlook (if it isn’t already present), and set its value to 1.
Outlook Express will display the Contacts folder in the default delivery store (Exchange mailbox or Personal Folders .pst file) in Outlook. You cannot direct the WAB to a particular Contacts folder, except by changing the default store.

To turn off sharing, set the value for HKCUSoftwareMicrosoftWABWAB4UseOutlook to 0.