This drive used to be my C drive. I sent the machine out to have the drive replaced with a larger drive, so I'd have more space. The tech who did the swap pulled all user data off the drive and installed it to my new drive. I would have thought he'd have copied it, rather than deleting it from the old drive, but I suppose it's possible he did delete it from the old drive.
But there's something more than that going on here. Chkdsk says there are files on the drive.
... but File Explorer doesn't see them ...
I'd try your idea, but I no longer have any burnable CDs. I haven't used any in years. I could go out and buy some, I suppose. Why wouldn't I just try installing Parted Magic on my C: and running it from there. Are you saying that in that scenario, Parted Magic would be reliant on aspects of my OS that may be causing the problem and that, therefore, it might not show me anything chkdsk and diskpart haven't?
CygWin is a Linux emulator. Basically any application that is available for Linux will run on CygWin (with, I imagine, some exceptions).