The DVD is a HP DVD 940 external drive that has a transforer in the cord.
My duplicate laptop drive is in a USB Philips external case that I know is working properly.
Long story that you should know. I had just downloaded the Vista64 MS updates (19 of them) then attempted to clone the drive as usual, using Acronis True Image. The clone attempt failed and the external hard drive is no longer recognized by Windows even in my son's computer.
Since that was my only backup, I was attempting to save my most important files to a DVD+RW using Win Explorer when I got the "this drive is read only" message. This was after I had already moved 1.5GB of information onto it from my C: drive.
Before I go with removing the 19 Windows updates to see if that is the problem, I want to have some kind of backup protection!