... cannot be opened for writing

Until yesterday, I was using mp3tag for a long time. I'm not sure, but I think I was using Mp3tag 2.64. Everyting seemed to work fine with it. Yesterday I upgraded my computer, and reinstalled Windows 8.1. Since then, Mp3tag 2.66 doesn't seem to be able to resave any music file types when I edit tags. When I run the mp3tag in administrator mode, it resaves just fine. I don't want to use in administrator mode.

As my music collection is on an old HDD, I thought the problem was in file ownership. So I repossessed the files even though I (user&administrator) was set as owner. In the options to choose other owners there were to enycrypted/unkonwn users, which were probably leftovers from old system. I did try to remove them, but the files still don't resave.

To me, this looks like a file access problem, but I don't know how to solve it. Could it be 2.66 related?

Can anyone please advise?

UPDATE: It seems that I am unable to rate files in File Explorer too. Also, simple c&p of files to the disk results in UAC asking for administrators permission to paste it anywhere on the drive. So there must be some kind of general file access problem.

UPDATE2: I just repossessed the entire drive as Administrator, and everything works now.