Can I erase or otherwise format a CD?

No. After a CD (Compact Disc) or CD-R (Compact Disc Recordable) is created, it cannot be edited, erased, formatted, or otherwise modified. If you've created the CD or CD-R and want to modify it, recreate it using a new CD-R.

If you're using a CD-RW (Compact Disc Re-Writable) disc, it can be modified. Information written to the disc is linear, which means if a disc file is modified, it must be re-written to the disc. The existing file on the disc cannot be modified.