I am having a lot of trouble backing up my files such as digital pictures, word docs, etc. I need to do this before I start go through the cleaning process and possible reformat. I am using an external DVD burner since the tray on my PC's CD drive is broken. I am putting the files on DVD +R and the process goes fine except when I eject the disc and try on another PC the files are not there. What am I doing wrong? Thanks.