Error Copying File or Folder message when copying file to CD
 

When attempting to copy my Excel files to a CD, I get this message:

Error Copying File or Folder
Cannot copy [file name]: The disk is write-protected. Remove the
write-protection or use another disk.

This occurs with every CD I attempt to use. I mostly use flash drives
to copy from one computer to another, but every time I do so, I notice
that that computer will no longer copy CD's afterwards. Since I don't
make illegal copies of software, I wonder if I've picked up something
that is transferable and is shutting down my computers' (3 now)
ability to burn CDs. Does anyone have a suggestion as to how this
might be remedied? Thank you in advance.

Michael