It seems like there's no file system recognized by the OS. This sometimes happens when you use a drive with a device like TV, DVR, PVR, etc. Try accessing the HDD via Ubuntu Live USB/DVD, to see if you'd be able to get to your files, or give it a go with data recovery software: http://pcsupport.about.com/od/filerecovery/tp/free-file-recovery-programs.htm.
Please keep me updated.