I have been using my cd-rw drive to back up data. the cd filled up today and I would like to delete some of the files to create some space. When I try to delete a file I'm told that it is a read only file and I can't delete it. This happens on all of the files. I tried to format the CD and got the same response. I tried using a blank formatted cd and all works well. Any ideas as to what is going on?