I'm not a huge fan of horror films, except for a few exceptions: movies about disturbed children, like Children of the Corn; zombie films, which have really become a genre all to themselves; and J-horror. Not sure why these exceptions exist, but they do, and it's the inclusion of the J-horror exception that led me to the Ring cycle. The first film, Ringu, was an excellent entry in the genre, with a bizarre premise, creepy atmosphere, and genuine scares. Unfortunately the prequel, Ring 0: Birthday (the subtitle of which is never explained), simply isn't scary, necessary, or even all that interesting.
If you don't know the premise of the Ring films, it is about a curse in which the a disturbing video tape causes its viewer to die a week later. This film is set 30 years before the events of Ringu, with the origin of the creator of the curse. Sadako, the antagonist of the first film, is now an innocent and beautiful 19 year-old member of a theater troupe. We get to see her before she became the evil entity we know and love, with her role of a simple girl who loves acting and is falling in love with another member of the troupe. It's interesting to see...for about 10 minutes. Unfortunately this is the first hour of the movie. Stringed throughout are mentions of tapes with odd sounds, the whole troupe being cursed, and the existence of a second Sadako, but none of these elements have enough done with them to have them either make sense or be scary; would have been nice to have one of the two.
The film does pick up in the last half-hour with the part of the story anyone who has seen Ringu already knows. However, while it is good, it's really not in any way necessary, since anyone watching it probably already knows the events that inevitably unfold. While it is interesting to see it from Sadako's point of view, making the story more tragic than it already was, it's still not needed. Unnecessary prequels can work, like in the case of Underworld: Rise of the Lycans, if they are entertaining enough, and bring enough new material to the table. Ring 0 fails on this account in that the only new material brought forth isn't very interesting.
I think a better approach to this concept would have been exploring the entirety of Sadako's life, rather than this small chunk, or extending it into how the curse was developed. What we get instead isn't horrible, but it is very disappointing. I like the idea of Sadako's origin story, but the execution misses the mark. It gets points for trying, and for providing a good final 30 minutes, but overall it's not a necessary view.