|A long shot at this point as you have tried a lot already I know..|
Consider using Kill Disk to totally wipe the drive. If I understand its operation correctly it will wipe everything of the drive - partitions and all. And a trawl via google seems to suggest that it will deal with the locked partition in the process - as in it will delete it too.
I'm also of the impression that one can selectively delete (kill) a partition too; but not having used it I can't speak from experience...
Possibly (hopefully on this occasion) others here are more familiar with Kill Disk and can possibly shed more light on what it may be able to do..
Be very aware that its operation does irrevocably delete data (partitions/logical drives); there is NO going back.
My feeling is that you may be able to achieve a total wipe of the drive; but I'm not sure.... As I say I have no personal experience with this utility - although I know it's wl regarded.
The faq here re' locked volumes does seem to suggest a possible workaround - but requires Kill Disk be run from a bootable media. Se bottom of this plink/page:
The manual here:
does include making bootable media to run the utility - section 4 onwards.
Which having said all of the above.. - if you're willing to wipe the drive fully.. Perhaps consider replacing it with a new one? A blank - and one hopes unlocked drive - will allow you to rebuild your system anew; and with minimum fuss? At this stage - considering the time and effort you have expended, quite possibly a new drive is the better path? Drives these days are cheap enuff?