There is a nameless folder in the Windows Explorer. When you try to delete it, you receive an error message like: "Not accessible".

Probably the name of the folder is too long.

Solution:

1. Open the command prompt.
    
2. Go to the directory where the affected folder is located.
    
3. Run "dir /X". This command lists the content of the folder using short filenames.
    
4. Run "rmdir /S short file name". This command deletes the specified folder plus all subfolders and files.