Have you ever encountered problem when deleting certain files with special characters or files containing question marks in the name? I had such problem before when I tried deleting those files. I didn't remember clearly how I got those files. But, I guessed that they were files with chinese characters as their names originally.
Usually files that can't be deleted using usual Windows delete command, can be deleted using third-party delete programs. Such programs can be found easily from search on google. I tried some such deleter to remove the question marks named files, but they all failed to delete those files. So, what can we do if those so-called deleter cannot delete those files? Do we have to move all movable files to another partition and then remove them by whole partition delete? Not really, there's another way which could probably solve this problem.
Try using a Linux Live CD and boot from it. Then Mount the drive with the files you want to delete. After that, right click on the files and select "Delete". Usually this will solve the problem. I have tried many times using Puppy Linux Live CD. It's a very light-weight linux distro. Try using Puppy Linux to delete those files with weird characters.