I never do a disk image of my C: drive. I always clone it to a completely separate hard disk which is then removed from the computer and stored. Very little changes on my C: drive so I only need to do it about every 3 months. If my C: drive fails I only have to put the cloned drive in as master and reboot. Then repeat the procedure again.
All my other drives and partitions are backed up regularly to CD and now DVD, again not with drive image but just using Nero and copying.