Includes Miku, Kaito, and Luka.
The original version, I believe was in Finnish:
http://www.youtube.com/watch?v=4om1rQKPijI
But then the song was attempted by the software: Vocaloid by the Japanese company Crypton Future Media. Vocaloid is voice synthesizing application based on voice samples of real Japanese singers.
http://en.wikipedia.org/wiki/Vocaloid
The most popular version is by Hatsune Miku:
http://www.youtube.com/watch?v=kbbA9BhCTko
But my personal favourite is by the somewhat less popular, but in my opinion way better sounding Kagamine Rin:
http://www.youtube.com/watch?v=mq-HMyxXMqM
(i would have included Rin, but the chibi look does not suit her. the wideness and the short shirt do not mix well XP)