Some people have experienced difficulties with activating the Windows Vista builds that we distributed at the PDC. Please accept our apologies for this; there's been a mismatch between the activation servers and the product key that was handed out. It's embarrassing - we screwed up - we're sorry. So here's the deal:

For Windows Vista Beta 1, use the following product key:
Q8WDJ-TR4KJ-X8WHM-GVGV3-H74C3
For Windows Vista Build 5219 (PDC CTP), use the following product key:
GKFV7-F2D9H-QKYXY-777P3-4M73W

If you are having problems activating either build, please try again tomorrow. We are replicating the needed changes as we speak, but at this point, not all the activation servers are updated.

On a more positive note, we've made it easier to get hold of the Office 12 Beta 1 release when it's available. Instead of having to go to Microsoft Beta Place and fill out a nomination survey, we will now automatically send it to all PDC attendees to make the process as hassle-free as possible.

Source: Tim Sneath's Blog