El Capitan: after installing OSX 10.11.3 I find that I have two iMovie iconds in Apps. Only version 8.0.6 will lanuch. What is wrong?

After installing OSX 10.11.3 I find that I have two iMovie icons in the applications folder. Futher, I understand that I can no longer use iMovie HD, which was my main method for video. Now, I see that my previous version of iMovie version 8.0.6 still works, even though I really only knew how to use iMovie HD. So, I try to open the more recent iMove installed with El Capitan and it will not launch and I notice it does not have a version number. I need to get back to video production. What are my options?