All files on a CD or DVD are automatically marked as "Read Only" because that is all that a CD or DVD is once it has been finalised.
Once the files have been copied to your computer the status can be changed, either file by file or in bulk.
If you have copied all the files to one directory, open that directory in Explorer, highlight all the files, then go to Explorer File - Properties. There is a box marked Read-only. I would suggest that you untick it and click OK and repeat the process to tick it, then untick it again. In my experience sometimes these tick boxes don't do quite what you expect if you have some files read only, some not.