I'm not sure how well known this is, but we did work in Windows Movie Maker and Windows DVD Maker to use the Windows Imaging Component (WIC) to make sure we supported images in the camera's RAW format.
I know some folks like to shoot photos in the RAW format and previously you would have to convert those files to JPG or something similar if you wanted to use them in Windows Movie Maker.
Well in Vista, if you've imported some RAW photos into your Photo gallery it will now give you the option to download the codec to support those files (every camera has it's own RAW format). I know the codec for Nikon camera's has been out for a while and Canon's was released not so long ago and there are probably other cameras supported too.
Once you've done that, you'll be able to view the photos in Photo Gallery and if you import them into Windows Movie Maker or Windows DVD Maker they will know how to use the photos directly as well.