When you first booted up your Mac, you would have been welcomed by a classy presentation with "Welcome" written in a bunch of foreign languages. Unsure what these videos are? Watch the demos at the bottom of this article. If you want to watch this video again, follow these steps for Tiger and Leopard.
Open up finder and Click Go->Go to folder. Type this in:
/System/Library/CoreServices/Setup Assistant/Contents/Resources/TransitionSection.bundle/Contents/Resources/
A folder should pop up, and two files should be inside:
intro.mov
intro-sound.mp3
As you can see, unfortunately they are two separate files. To fix this, simply put them both in iMovie and watch it that way. You may need to trim the audio track as it may go for longer than the video!
For a demo, here are two video files (click the image of the video you wish to see):

Thanks to Annie for the Tiger video and audio file.




