If it is the second blank disk that you insert when instructed to, it might be defective, already used or the wrong type. You only can use write once dvd's--not RW rewritable ones. Try another disk that is a diff brand.
You should not only depend on Dell backup and recovery--especially the free version since it is very limited. Make additional backups and system images using Windows backup/recovery program as well as recovery/repair disks. Search for Recovery in Control Panel. DVDs should not be used at all since they can be unreliable, lost or damaged. Buy an external hard drive for backups and system images and 16gb or bigger flash drives to use as boot drives.
Copy your personal files instead of just backing up because backup programs cannot be used on other windows operating systems on other computers. Copies of files can be used on any operating system.