Shareaza

There are two problems here:
1) Shareaza sometimes incorrectly marks a file as ghost. My understanding is that the only way to make a ghost file is to either: 1) cancel a download and choose the ghost option, and 2) delete the file from within Shareaza. Since I never do either 1) or 2), I shouldn't have any ghost files, but Shareaza seems to think that the file was deleted while actually I've merely moved it to another folder. Maybe there's something I don't quite get here.
2) Once the file is marked as ghost, how to remove it from that list? Since it actually exists in the library, deleting a ghost causes the file to be deleted too, which is not what I want. If I save a copy of the file, delete the ghost, then return this copy to its original location, it's again marked as ghost.

I'm not sure whether I've understood correctly what you said, but normally, deleting a ghost file in the ghost files folder of your library (inside the Shareaza library manager) should not delete any file on your hard drive...

Also, you forgot a third option: A ghost file is also created when Shareaza detects that a file that was previously there has been removed from Shareazas shared folders, because Shareaza supposes this file to have been deleted.

This third option appears likely.

For some reason all of my ghost files display locations that are within library folders. Maybe I moved the files outside the library folders, making them become ghosts, then put them back, and they are still marked as ghosts. Since the purpose of ghost files is exactly not having to keep them in the library, this perhaps does not make sense.

I've tried do delete one such file from Organiser->Ghost Files by pressing Del. The file actually was deleted from the HD (remarkably, without any warning), and appeared in the Recycle Bin. After restoring it from the Recycle Bin, it did not, however, reappear in the Ghost Files folder, so I guess this is the answer to my original question.

When one right-clicks an entry in the Ghost Files folder, one of the options is "Delete", illustrated by a small recycle bin. Not sure if that was the original intention, but it actually does what it advertises.

My suggestion would be:
- Remove the entry from the ghost folder if the corresponding file appears in one of the regular library folders.
and/or
- Don't actually delete upon pressing Del in the Ghost Files folder. Don't call it "Delete", but "Unmark" or something like that.

Sounds like a bug to me. My totally random guess is that being a ghost rather than a real file is a flag in the library entry and the code for adding file forgets to clear the flag. That would explain all the symptoms, anyway. Have you tried "Rebuild" for the folder the files are in? Have you tried moving the file, deleting the ghost, closing and restarting Shareaza, and then adding the file back?

Did not try any of these. I've cleared the Ghost folder by deleting, then restoring from Recycle Bin - so far so good. It's a minor annoyance, but someone might want to take look at it.

Ghost files is just a history log of missing (deleted, moved, etc.) Library files. They have no real files behind but saves all metadata except thumbnail. You can clean ghost files one-by-one by clicking Delete button, or clean whole Library by pressing Settings -> General -> Library -> "Clear History Now' button.