Thank you Daniel. It's a simple answer, but things don't seem to be resolved.
I put the SD card in the computer's SD slot, and went to finder, to copy the files to a folder on my desktop. The contents of the SD card showed up as folders:
DCIM (empty folder)
Private>AVCHD>AVCHDTN>Thumb.tdt, and Thumb.tid
BDMV>CLIPINF, INDEX.BDM, MOVIEOBJ, BDM, Playlist folder, and Stream folder
IISVPL folder>empty folder
In other words, his folders all have "stuff" in them, but the movies themselves don't appear to be there.
Yet, when the SD card is in the camera, I can see all of the videos he has recorded for the past 3 years.
I'm starting to wonder if this is more than a PC/Mac issue, and if there is something wrong with his card files. My friend has also had trouble getting his video files from his own camera onto his PC(that's why he has asked me for help). Just chalked it up to his Windows operating system being difficult-lol.
Seems like something might be wrong with the card, maybe? Then what? Media recovery software?