My friend needs to create a video and she has some source files that are .MOV format. I assume they are h.264. She can view the files with QuickTime. She has a laptop running Vista, and a just-downloaded version of Windows Live Movie Maker (which I'll call LMM for short). LMM shows an 'X' icon when she tries to add one of these files to it. My machine runs Windows 7 Pro, and a slightly earlier build of LMM and has no problems editing video with these source files. I assume she's missing a codec but what can I tell her? I've looked at the answer that mentions a QuickTime DirectShow Source Filter Plugin. It mentions only playback through WMP, not editing via LMM, but is that what she needs? I didn't have to load anything like that. That project's now done (she punted and used iMovie on a Mac). But I did gain another clue. She could play a 720p .MOV file, but these were 1920x1080 files.