How do I delete a project in iMovie 9.0.9

When I open iMovie. I have a list of projects, some of which I want to delete. When I look in User>Movies>iMovie Projects I see more files than are listed under the Project Library in iMovie. For example, one major project has 4 different segments listed under Project Library, but there are 7 files related to it. The files have extensions of .rcproject, m4v, and mov. There are 4 files with the .rcproject that correspond to the projects listed in the Project Library. I assume that I can move these to the Trash and delete them. Is that safe? Is there any way do delete them from within iMovie? Where did the .m4v and .mov come from?