In your Documents folder is a folder called "Microsoft User Data". Within that folder is a folder called "Office X Identities."
When I want to move my Entourage from one computer to another, I copy my Identity folder between them.
The folder is "locked" on login- so you actually have to pull the old one out, move it to trash (or a safe backup place), and move the new one in. Then, logout and log back in to enable the replacement folder.
If there is an easier way, I'd love to hear it! My identity folder is hovering around a gig, causing me to hook up the TiBook to the 100BaseT hub when I want to transfer (AirPort would take forever).