If you switch your Outlook installation to "Corporate/Workgroup" mode, the
problems accessing the WAB will go away. There may be other issues you'll
encounter with Outlook 2000 on Vista, but the WAB issue won't be one of them.
At least you'll be able to import the Windows Mail contacts.
Corporate/Workgroup mode won't allow you to use an IMAP account, though, so if
you use gmail and IMAP, you'll be out of luck. gmail and POP, however, is an
alternative.