Previously mentioned as being used to completely restore a broken system using partition images was Clonezilla, so it seems like a good idea to post up a short guide for using it!
The First Step: Download the iso from here, you're looking to download the one marked as 'stable iso/zip'. You can then use a program like Infrarecorder (Windows) or K3B (Linux) to burn the iso image to a blank CD. Alternatively, use USB Startup Disk Creator (Ubuntu - System > Administration) or UnetBootin (Windows) to create a bootable USB drive.
The Second Step: Check your bios settings to ensure that your USB or Disk Drive is listed above your HDD in the boot order, else Clonezilla will not initialise upon bootup.
The Third Step: Have your backup medium ready, be it USB Stick or External Drive, but do not plug them in yet. Boot the computer, you should be presented with a menu looking just like the one below:
Rest of the guide after the break:
Boot menu choice: In the image above you can see the boot menu choice, you want to be selecting to top option labelled 'Clonezilla Live (Default settings)'.
Select Language: You'll then be presented with a language screen, select yours.
Select Keymap: Default will do, however you may as well go in and select the one appropriate to your keyboard and country.
Select Mode 1: For this guide we are creating an image of an existing drive. Option 2 would be for straight disk to disk copies.
Select Clonezilla image directory: This is where the image is to be saved to/read from, in this guide we'll be backing up to a secondary hard-drive installed in the machine, however, If you're backing up to an external USB medium then you'll want to select the same option - local_dev
You will now be prompted to insert a USB device if you want to use it, plug it in now - wait for it to be recognised and the next prompt to pop up.
Select the device to be read from/save to: - This is where we'll be saving the image to. In this case it's going to be the secondary hard-drive (hdb1). For you it may be an external USB device, it should show up in this list for selection.
Select Directory: This is where on the drive your image will be saved to, toplevel will do just fine, however if you have a specific folder in mind, here is where you can select it.
Select Beginner Mode: Unless you have very specific requirements then you do not need to explore expert mode, beginner will do everything you want just fine.
Select savedisk: In this guide we're looking to back up an entire hard-drive, so savedisk is the option we want. If you are looking to make an image of a specific partition on disk then you should select saveparts.
Input a name for the image: This can be whatever you want, the default is also fine.
Choose the disk to image: In this case it is the primary hard-drive which is typically going to be hda or sda.
At this point you will be asked if you wish to continue, if you're happy with the way it had been set up so far then press 'y' and hit enter!
Away we go: You will now be presented with a screen showing progress and estimated time to completion like this:
Done: When this has all completed you simply need to select to appropriate option from the quit menu. Typically you're either looking to press '0' and then enter to poweroff, or '1' and then enter to reboot.
Check the image: See that it appears on your backup medium. It should appear as a folder full of a few archives in the directory you previously selected. Here you can see it appearing in the empty hard-drive this Windows 7 virtual machine was backed up to.
If you run into any errors or have questions then feel free to drop a comment!