I haven't reinstalled iLife since replacing my HD, so I suppose I can try that. I've installed Perian so that QuickTime can recognize xvid content. I'm guessing that without QT recognizing the format iDVD wouldn't be able to either, right?

Will iDVD do the transcode? I haven't used it in ages, but I thought it had to receive MPEG-2 content to do anything.