copying onto a CD for backup

I copy the same file (names) onto a CD-RW (formatted for
dragging)thereby overwriting what's already on the CD.
The problem is, since I rebooted for another reason, I am
no longer asked "there's already a folder called ____.
Do you want to replace it?" It just copies. Where can I
change this so I get asked each time when I'm overwriting
a file with the same name? Thank you.