A week or so ago, I posted an updated product key for the Windows Vista builds we distributed at the PDC. We've been keeping a close eye on attendee feedback to make sure we've mopped up any problems people have experienced whilst installing Windows Vista. In general, people seem to have had no problems once they used the correct key. However, a small percentage of installers manually extracted files from the ISO image with a tool that didn't handle long file names well, and they hit a further problem as a result. James Adams (an SDE in the beta team) has posted a note to the beta newsgroup which I've reproduced here for visibility to a wider audience:
For those of you who have been trying to install the new build but have been encountering a message saying that your product key is invalid, we've figured it out.
Vivek Mukherji identified the root cause of this, and we have verified it. As such, we've got a workaround for you. If you are using a utility for extracting files from the ISO which has a setting for preserving filename length in the files you're extracting, you will need to enable that setting. This will solve your problem.
[UPDATE: Removed text about manually renaming files, since this simply replaces one problem with another.]
If you're unsure if you're experiencing this issue or not, check out the c:\$windows.~bt\sources directory. If you see a file pkeyconfig.xml there, the ISO images were extracted successfully. If on the other hand, the filename has been truncated to pkeyconf.xml, you'll hit this problem. One tool that some people have used with success for ISO image extraction is Daemon Tools. I have no direct experience with this tool and cannot therefore make a recommendation.
Drop me a line if you're still having problems, and we'll see what we can do to help, but I think the combination of this with the correct product key should resolve all the outstanding issues. I've updated the wiki with this new information.