Windows Explorer has problems with certain media file types (e.g. AVI files with unknown encoding) when it attempts to generate previews. As a consequence, such files cannot be deleted or renamed within the Explorer. A simple workaround for this nuisance is to display the desired directory in a dialog box, select the desired file and then delete or rename it via the context menu of the dialog box (right-click, Delete or Rename). Alternatively, you can unregister the DLL that causes this problem [Register].