in my experience i was the same as a hard disk from a broken xbox 360, which i now use in an external enclosure.
the hard disk shows up in windows with either a fat32 or ntfs partition which is empty.
a deeper look with a hex editor shows unequivical evidence of actual data on the disk but getting to it nigh on impossible without using (or writing) a programme specific for the task.
if you plan on extracting the data, by all means waste the time but in the case of the Sky Plus content, this can all be downloaded in half the time (and possibly twice the quality) using your favourite bit torrent client.
if you wish to recycle the hard disks from the poor dead devices, as i have done, a hard wipe of the disk and the creation of a new partition in your favourite file system is more than recommended.
be aware though that some disks have firmware installed forbidding this, which was the case with a Micro Drive (with a compact flash interface) which i pulled from a Creative Zen MP3 player in 2008, windows - even acronis, would not lick it.
For the record, the 500gb samsung came from a white 2009 model SKY+ HD box, it's model number i do not know, but it is my understanding that the 80GB model inside the Black SKY+ (non HD) box also uses a SATA interface, since SATA was rapidly becoming widespread since 2006 and the Black SKY+ 80GB box is a 2007/2008 model.