It's apparently the ORIGINAL video that Nintendo posted online during E3 2003. Weird thing is that I do remember downloading the video from Nintendo's E3 2003 site :lol About 2 days later, Nintendo replaced it with this video http://web.archive.o...ie/metroid0.wmv
After doing some more digging, I constructed a simple website to host my findings
I've posted the information below for convenience. Oh & if anyone still has the original video saved on their computer, or knows where to find it, please shoot me a PM. It would be great to have the original video instead of a copy of a YouTube video.
At E3 2003, Nintendo announced a new Metroid game for the Game Boy Advance: "Metroid: Zero Mission". It was a retelling of the original Metroid game. As with all games, the earliest released footage/screenshots will almost certainly be different from the final game. With this case, however, we accidentally got a glimpse at an earlier build of Metroid: Zero Mission.
When Nintendo uploaded the screenshots & trailer to their E3 2003 sites (Nintendo of America & Nintendo of Japan) (guessing the date was May 13 by the screenshot filenames), they accidentally uploaded this video
(This video was found on YouTube. In my searching, it looks like it is the only copy out there.)
(Chibi Samus can also be seen in this piece of Kraid concept art courtesy of the Metroid Database & the japanese Metroid: Zero Mission site.)
(I myself remember watching this video & wondering why it was so different compared to the screenshots that Nintendo released.)
While doing more searching, I came across a Newsgroup topic (from May 14th, 2003) that seemed to highlight the confusion between the screenshots & the first video that was posted. In the topic, it links to a Gamesarefun.com article that describes & links to the video (trying to see if they still have a copy) (here's a link to the Wayback archive)
As a comparison, here are the original 9 screenshots that Nintendo released on May 13th, 2003, along with the first video. (Credit to IGN). While the are watermarked, they are the highest quality screenshots that are still on the net.
As you can see, the first is a much different version of the game compared to the one shown at E3 2003 (even very different compared to the 9 screenshots released at the time the video was also release.) It's obvious that this video being uploaded was a mistake because, on May 15th, 2003 (a few days after the original video was uploaded), it was replaced with the following video (on all Nintendo E3 2003 sites).
The only example that I can find is from Nintendo of Japan's E3 2003 site (and the Google Translated version)
The following is the video that Nintendo replaced the previous video with. It was located via The Internet WayBack Machine's archive of the file.
While the content is mostly complete, the formatting of the site isn't 100% set in stone. I wanted to created a simple website for the information until/if I find anything more.