If it's like most torrents, you have to extract it. You should have a folder full of .rar files. Download a program such as "WinRAR" and once installed, right click on "____01.rar" and choose "extract." It will then create a .mpg/.avi/.whatever file that will be the watchable file.
TV-Nihon doesnt use RARs, so the obvious question should be, did you already downloaded the video, using the torrent file, or all you have is the "whatever.torrent"?
Download BitComit or any of the myriad BT clients... then use it to run the file ["whatever.torrent"] and it'll download the actual video onto your harddrive.
Well, not everyone knows how most torrents work. Now, I wasn't aware that TV Nihon doesn't use .rar files. If it's a "____.torrent" file you have to open it with a BitTorrent client. I recommend Azureus.