So I've never encountered a problem quite like this before, and I genuinely can't even begin to figure out how to search for it. I've tried but, you know, so I apologize in advance if this has been discussed before.

I have a HDD that began showing basic symptoms of early-stage failure. Bad sectors, hangs during loading times, but what tipped me off was a particular series of events. A rather large game update failed to download, and the first attempt I made to run a disk check and filesystem repair never finished and instead crashed the system after the monitor went on standby. Reboot resulted in the OS telling me to repair it with the installation DVD, so I did, and after supposedly successfully accomplishing this, told it to run a disk check and filesystem repair prior to startup. Reboot. Disk check never initiated and boot up locked on the splash screen. Had to force reboot. OS told me to repair it with the DVD again. Repair environment hung on initial scan following repair command. Force shut down. Fired up KNOPPIX. Simply opening the Disk Utility revealed I had over 200 bad sectors on the drive. Immediately I knew it was boned. Stupidly were it not for Microsoft having incredibly appallingly unstable software, I would have been suspicious a lot sooner. yes this was windows and i really wish i never had to pick it back up again (I was pure Linux for a couple of years)

This happened... three days ago. Instead of trying to repair the filesystem via KNOPPIX (actually I couldn't even get it to mount any of the partitions on that disk at all), I opted to get a replacement drive and just clone the data on the failing one to the new one when it arrived. At the time I had shut it down from KNOPPIX, everything could still see this drive. I left the machine containing this abhorrent thing off until the new drive arrived and I could plug it in via enclosure (it's a laptop) and proceed with the cloning. Normally I never turn it off. Cut to today. The instant the new drive hit my doorstep I was testing it on another machine to make sure it worked and went straight to setting it up to clone.

Already as soon as the machine made it past POST I noticed something was amiss. The readouts I was receiving were definitely not the same ones I was watching just a few days ago. I started with Ubuntu Live at first pretty much entirely because it booted a little quicker. When I ran 'fdisk -l' in terminal (as root, of course), Ubuntu couldn't see the original HDD at all. Not entirely sure what to think, I decided 'well okay, I'll swap to KNOPPIX then'. As a precautionary measure, before getting all the way into KNOPPIX just to reboot again, I decided to check the BIOS. The drive no longer showed up on the main page, but checking the SATA configuration menu showed that the BIOS knew it was still there in some fashion.

I ran 'fdisk -l' as root again in KNOPPIX, and what came back was somewhat curious. I have three drives connected to the laptop: the original HDD, which would normally read as 'sda', the USB stick that KNOPPIX and Ubuntu Live were on read as 'sdb', and the replacement drive reads as 'sdc'.

Ubuntu read the USB stick as 'sda' and the replacement drive as 'sdb'.

KNOPPIX on the other hand, while also only coming back with two drives, assigned the USB stick as 'sdb' and the replacement drive as 'sdc'.

I have not attempted to do any data transfer or cloning at all. Once I hit this bewildering snag I stopped and did my best to try and research what it means and if I could still try to clone the failing drive.

...This is ridiculously long-winded just to ask a question, wow, sorry. I'm really bad at summarizing, actually.

I guess I have a couple of questions:

What does this read discrepancy mean?

and:

Is it still possible to salvage the data with the tools provided in KNOPPIX, or is it beyond hope?

Part of me is still holding out that I won't have to ship the blasted thing off to become an extraordinarily costly bill, but at this point I'm not holding my breath.