Are you sure the torrent is finished downloading? You have to wait for the files to finish. Usually, your torrent client will say "Uploading", or "Seeding", or something along those lines, once you're finished downloading it.
I know it's quite a few months too late but- I am guessing you are using Bittorrent and so all you need to do is right click on the green bar and click open directory, then play, install or use the file however is necessary. It is not neccessary however to seed the file before you open it. So I guess this is just a bad file.