Our regular listeners hear us talk about this subject often, but it bears repeating as much as we can talk about it for your data's safety and your sanity. Backing up to CD's is a multi-step process and all the steps need to be followed for it to go right.
CD's work great for archiving data that won't change. This includes pictures, music, your finished novel, etc. CD's should only be burned ONE time. CD-R's have the capability of being written to many times, but this also increases the likelihood of problems with the CD. Burn them once and store them in a safe place.
CDRW's should NEVER be used for any purpose.
The reason we don't like to use CD's for reusable backup is a technical one. When we burn CD's, the CD burning software has to burn extra files to the CD called a Table of Contents (TOC). These files act as the disk's librarian. When inserted into a CD drive, the drive looks first for the TOC so it knows how to read the disk and recall the data. When repeatedly burning the disk, the software has to find and read the old TOC, create a new TOC (that ignores the original) and burn it to the CD. Too many chances for error can occur in this process. We know that many people have had no problems burning CD's and CDRW's multiple times, we just want it to be known why the disk fails using the process.
For data that changes often like word processing documents, financial program backups, genealogy backups, address books, and other similar files, we recommend using USB flash drives. They are fast, spacious, and durable. Copying information to a Flash drive is a one step process versus the multi-step process required by CD burning.
As always, if you have extremely important information that you really don't want to lose, make multiple copies of your backups.