For a new page... anyone?
It comes down to your drive having corrupted/lost it's File Allocation Table or the journal for it depending on what format the disk was in before.
Imagine your hard drive is a massive library, with the files on it being books, but there's millions of books everywhere, it would be a complete mess and you'd never find anything. However you've got an index (the allocation table) so that you know where every part of every book is. There's multiple copies of this allocation table in the library, so you've got backups.
Whenever you create/move/edit change a file, you need to update the allocation table and then update all of the copies, if you lose power/pull the drive whilst it's updated say 3 of the 6 copies, how do you know which is the correct one?
In short it comes down to something corrupted the file allocation table in a way that it wasn't recoverable, so you've now got files all over the place and no way to work out where they all are.
In short the recovery program will look at every sector on the disk and work out where it's from and what file it belongs to (this is why it takes soooo long to scan as it needs to read everything.)
It's an interesting one, and it's rare, but it can happen (This is the main reason of why they say you should eject a USB drive as it makes sure all of the copies of the index are correct and up to date. (Plus all files are closed etc)
It's in interesting one, and it can happen, but it is rare. In terms of what caused it, it can come down to a few things, some mechanical (meaning you should change the drive), or it could have just been a power loss and you've been unlucky. I've seen drives like this go on for years, however, as with anything like this, I'd say replace the drive, if your documents etc on there are worth more to you than the price of the disk, replace it.
Hope that makes sense, if it doesn't just let me know.
