The 5D shoots not-quite-standard AVCHD encoded video in a .mov container. Your friend can play it on his Mac because he has the camera, FCPro and the Canon 5D plugin for FCP.
In addition, copying only the .mov or .mts files from an AVCHD camera is a common error. With AVCHD video, you need the +entire folder structure and files+ from the camera's memory card - they are needed to capture or play back the video.
It's possible that
Clipwrap may be able to convert the files for you, but it would be better if your friend converts the video to +QuickTime/Apple Intermediate Codec+ or
QuickTime/ProRes422 for you. You should then be able to play it in the QT player on your Mac.
Note: QT ProRes422 can be played in the QT X player on Snow Leopard but cannot be edited in iMovie or Final Cut Express.