You have to erase existing CD-RW data before the CD can be rewritten.
Erase the entire media or just the last session on the CD by selecting one of the following:
Erase the last session only.
$ cdrw -d cdrom0 -b session
Erasing just the last session with the -b session option is faster than erasing the entire media with the -b all option. You can use the -b session option even if you used the cdrw command to create a data or audio CD in just one session.
Erase the entire media.
$ cdrw -d cdrom0 -b all