I also doubt the drives have failed, but, they are 2 years old and maybe with updates on my Win 7, 64 Bit they no longer work.
I did try a new drive but it was the same. I needed a DVD-rw on my backup computer anyway.
I have already tried uninstalling the drivers and re-installed the drivers but no change.
I also deleted the files in the registry as suggested but no change.
i can still write music to the cd but no data, no format option in the properties and it shows as a CD-R in My Computer.