I covered a lot of this command in the link above because dd can be used to both backup and restore system data. It is the most effective way of doing a good backup, but you will have to used it to back up using this command as well and stored the data in an archive file. (usually .tar.gz)
Please read and double check these instructions as you could damage your system even further if you don't know what you are doing as dd is a very advanced utility!
In order to restore your image, you will need to boot into a Live environment (LiveCD, LiveUSB, etc.) and gain root access. Then you will need to work out where your hard disk is located on the file system. In order to do that run the following command:
This will now show you where all of your disk drives are located. Once you have found the one that is your hard drive keep a note of where it is (/dev/hda as an example). If are not running the command as a root user it will not return anything.
The next thing to do is run the dd command itself and let the restore commence. In order to do this you will need to be able to access the image I mentioned earlier and have the hard drive unmounted. If it is mounted, just run: umount /dev/hdx replacing hdx with where your actual hard drive is on the system.
dd if=/path/to/image of=/dev/hdx (Replace hdx with your hard drive- incorrect placement could screw your system over royally!)
This will take some time because it's a bit-by-bit copy, so go and get a coffee or two :)