So if I'm undertstanding you correctly Deb, originally you were trying to burn the project to DVD while the raw video files were on an SD card connected to your computer. I'm not sure anyone would have had success this way. Most of us transfer the raw video files to a more functional drive (My Book works great) on our computer before beginning a project. SD drives are mostly used for transferring files & also some limited functionality (view pixs,docs,etc,)
Once you had the files moved to My Book & redirected the file path so PD could find them, it sounds like burning became easy.
Glad to hear you are things are going better for you.