Agatha Christie, And Then There Were None?

I read this book and loved it. I also saw the movie adaption entitled, "Ten Little Indians." The problem is, why can't I find this movie anywhere? I've searched at the library (where I first rented it) and various video stores. I looked it up online and saw that there was more than one film adaption, so I'm not sure which one to buy. Is anyone else having this problem?