How to retrieve vidoe from security camera hard disk

Hi,
I recently replaced a hard disk for a security camera cos it was full and have tried plugging in the full one to my PC to view/retrieve the videos but all I see are files like: BLK000002, BLK000003 and so on but no video files. Would really appreciate if anyone knew how to go about in retrieving the videos from the PC. The file system for the hard disk is ext3 (linux) . I can access it from the DVR btu what I would like to do is accessing in from the PC.