[ubuntu] Accessing/viewing video from a security system

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http://ubuntuforums.org – A friend has a local gas station/convenience store. He has a security system in place that records video. He has tried moving the video files to his Ubuntu PC to gain more space on the security system and to review them. I've haven't gotten to see it (I can understand - it's his security system), but he has told me he has tried a USB drive but couldn't see the files in Ubuntu - what ever that means, he has tried a cable USB connection (I don't know if it's a crossover cable or not). He claims he cannot see them at all. I've asked what file type they are but he just says security videos. (Hardware)