If you are backing up to DVDs try backing up to a HDD partition (not your OS partition). Ideally use an external HDD and use "Change Settings" to point the backup to a new partition location. Untick the make an image box.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Own build
OS
Windows 7x64 Home Premium SP1
CPU
Intel i7 2600k
Motherboard
ASUS P8Z68 Deluxe
Memory
G.Skill Ripjaws (DDR3-1600) 2x4GB
Graphics Card(s)
Nvidia GeForce GTS 450; Intel HD Graphics 3000(GT2+)