If you are having trouble with your Vista beta 1 (see my note on it here) that you received from the PDC, Microsoft sent this note around in an email regarding the PDC:

Windows Vista Product Keys - some people have experienced difficulties with activating the Windows Vista builds distributed at the PDC, due to an error in the product key that was handed out. Please accept our apologies for any inconvenience this may have caused. We are currently replicating the following updated keys to the activation servers; this process should be complete within the next 24 hours. { Note: updated keys are in the email }

I have to give Microsoft credit for rapidly following up. The email was full of good info on product releases and betas, etc.