"I have a Samsung portable hard drive which, for no apparent reason, one day decided it'd cock up. I can view my video, image & music files through the PS3, however when I plug it into a PC it tells me I need to format it, when I plug it into my iMac, nothing happens"
See why you need a "backup of a backup"?
First off, I suggest you get another drive. You'll need it for file recovery, and it should later become a "dupe" of your external-storage drive.
Get one of these:
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=USB+SATA+dock&x=0&y=0
(various items shown, pick the one you like)
And also get a "bare" drive to use with it. I recommend newegg.com for a vendor, and Seagate for the drive itself.
Next, go here and download the free demo:
http://www.cleverfiles.com/
For the time being, Disk Drill is free to use (in beta format). It just might do what you need.
Alternative:
Get either DataRescue3 or Stellar Phoenix Data Recovery. Both have good reps for getting data back when you can't access it any more.
Then,
- put the bare drive into the dock, plug it into the Mac, use Disk Utility to initialize it.
- DO NOT use a "PC-format" for the drive. Use either GUID or Apple Partition Map.
- Then, hook up the problem drive.
- See if the file recovery software can "see" it. If it can, see what can be recovered. Note: when doing data recovery, you need to leave the problem drive "untouched" (i.e., not "written to"). That's why you need a "scratch drive" to which the data can be recovered.
ABSOLUTE LAST RESORT:
If you can't get the problem drive to "mount up" on the desktop, you can RE-INITIALIZE it (yes, exactly what I said) to get it to mount, and then give the file recovery apps another go at it. IMPORTANT -- do not, DO NOT "zero out" the drive. Re-initializing replaces the drive's _directory_ but does not harm the data on it (again, unless you zero out that data). If you choose the zero-out option when reinitializing, your data WILL be GONE.
Once you get it to mount, the file recovery apps _ignore_ the new directory, and go right to the actual data sectors on the drive to find, scavenge, and then re-assemble the data into actual files. You _will_ lose all previous "folder hierarchies", since they were a construct of the original directory. But the files themselves will be there. You may discover some files have also "lost there names" (having nothing more but cryptic number designations), but they will still be usable. Yes, it's considerable work to figure out what they are. Data recovery ain't easy. But it can be done.
Final thoughts:
If and when you get the data off the problem drive, you want to save it to a backup anyway - reason I mentioned the USB/SATA dock first. These are VERY handy devices to have on your desk or in a nearby drawer.
STRONGEST SUGGESTION:
Do not, DO NOT use a hybrid Mac/PC format (such as "Fat32") for drives on which you intend to store important data from the Mac. USE THE MACINTOSH FORMAT ONLY (shouting intentional). Yours is but one more example of folks who probably buy a drive that was already hybrid-formatted, use it with both a Mac and PC, and, one day while mysteriously connected to a PC, the "Mac side" of the drive just goes.... POOF!
Keep a completely separate drive for "cross-platform" use, but again, keep your Mac stuff on a "Mac-only" drive!
