("suings" from my previous reply was jokingly directed at Microsoft, who apparently (according to that broken image) said that sudden interruption of the encryption process wouldn't wholly damage the data on the driver and that you can turn the encryption back on again later, by the way.)
But guess what. I've installed Windows 8 this morning aaaaaand the repair tool (from an old post of yours - THANKS!) did in fact work, and it goes as follows for the people who might encounter the same problem in the future:
cmd > Run as Administrator > repair-bde F: D: -pw -F
F (first one; leave the second as it is) = letter of the partially encrypted/damaged drive.
D = parallel empty partition/drive (same size or bigger).
It will then ask you for the password (which will be invisible as you type it in) and will start decrypting once you hit enter (at least in my case and as shown in the link below).
You can use the recovery key instead (works in different OS systems as well) if you have it but it has a different syntax, so check it all out here:
http://www.eightforums.com/tutorials/21433-bitlocker-recovery-unlock-drive-windows-8-a.html
http://www.eightforums.com/tutorials/21714-bitlocker-repair-tool-recover-drive-windows-7-8-a.html
(Please correct me if I got anything incorrect here. As I said, I'm a total newbie who I think got lucky, ha!)
Imp. notes:
- For those who are trying to recover from a partial encryption induced damage, the decryption/repair process will be 'stuck' at 1% for a good while prior to kicking in (could remain considerably slow depending on your setup, but will be progressing) - so be patient! I was panicking (yet not surprised) initially and even found some old forum threads from people facing the same (nonexistent) issue that received little to no help and gave up on their data just like that. I don't blame anyone, this can be a really misleading 'issue' (especially that a hanging error in this case will mostly likely seem familiar). It took me about an hour or more to see progress.
I'm still at 68% myself, but I'll keep you updated. It's progressing as I write this.
- I unintentionally alt+F4'd the Command Prompt earlier but there wasn't anything different from the first time when I turned it back on (same for the error below), so don't panic if it happens to you. However, be careful, because as made clear; it takes a good deal of time to see progress.
- I got an error (seven duplicates with different numbers) when I reached 7% reading: "LOG ERROR: 0xc0000037
Failed to read sector at offset 37571010560 (different number for each) <0x0000017>"
but it continued normally after that (again took a while, but it did proceed on from 8% as it should - no cutoffs).
I'm going to guess these are only a few irrecoverable files (will probably be partially decrypted to the empty partition/drive) that only took part in between 7-8% so it shouldn't be a biggie (will update you on this too) or make you close the Command Prompt just yet. Patience is key - I've been sitting here for hours but it's gradually getting faster as I write this. It's sure worth it and I still wouldn't believe my eyes to see it reach 100%.
- See you soon.
EDIT: I'm writing this from phone so I didn't post any pictures, but will sure do in the next post.