What format is the video? You shouldn't have to convert it.I had to download Iskysoft Video Converter to open a video sent from Windows.
when i tried to open it a drop down menu said that QT needed more media.In order to find out, what may be wrong with your video, you can use the following three applications to analyse the video file.
When done, you can use the "Report" (VideoSpec) and "Export" (Media Inspector) button to export a report,
attachable to your next post via the Image button.
In MediaInfo you have to go to the Menu Bar, select View > Text and copy the text via CMD+A > CMD+C and paste it via CMD+V into your next post.
If it is a WMV file, either use VLC Player or Movist or install Flip4Mac to play that file in QT Player.
when i tried to open it a drop down menu said that QT needed more media.