Hello, my name is Rusty. Sorry to hear you're having a problem, we're going to have to try to fix the file, as it seems to have gotten corrupt. Click here. VLC will fix corrupted video files. Install VLC, but be careful on the install. You don't have to install anything but VLC, and you don't have to accept any offers, just the license agreement to install it. Open VLC, and open your video file. It may give you the option to fix the file, accept that option. Please tell me the results.
You are welcome. The most important thing at this point is to copy the file to your desktop so we can work with it. Make a copy of the file so we have a backup in case something goes wrong. VLC should fix it. It may have parts where the video breaks up, that's where the file was damaged and where VLC did what it could to patch the video together.