Hard disks are often the first thing to die in a computer, so it is important to be able to quickly and easily migrate your data from one disk to another without having to reinstall your operating system, OS updates, and all of your applications, restore your files, etc.
Between hard drives that are about to fail or just out of space, I've been reaching for my Clonezilla CD an awful lot lately. It is a bootable CD that gives you the ability to image a drive or partition or clone a drive/partition directly to another (similarly to Norton Ghost). It also has the ability to add a clonezilla bootloader to whatever you clone your disk to, so the clone itself is bootable and ready install your disk image to any number of drives. This is super handy if you want to make a custom restore DVD for, say, a new laptop.
It uses an ncurses interface, so you will have to tab through the fields and use the space bar to press buttons and select options, but it does a good job of walking you through the process and is actually quite intuitive. It can and will save you a ton of time if your hardware is failing but the your software setup is just fine.
I had a somewhat unorthodox use of Clonezilla this evening which prompted me to finally blog about it. I run Windows XP in a virtual machine using VirtualBox, and when I initially set it up (a few years ago) I only allocated 10 gigs to the virtual disk. This evening I went to install some development tools on the XP VM and ran out of space. VirtualBox didn't have the interface for expanding the disk (that I could find; someone please set me straight on this if I am wrong), so I was in a bit of a pickle until I remembered Clonezilla.
I created a brand-new 100 gig VirtualBox virtual hard disk and attached it to the XP VM. Then I mounted the Clonezilla ISO file (which I happened to have lying around) as the CD rom drive and booted the VM into Clonezilla. Clonezilla saw the old 10 gig hard drive and the new 100 gig hard drive, and I simply directed it to clone the entire old disk to the new disk. It took about 15 minutes and when I was done I simply removed the Clonezilla ISO and the old drive from the VM, fired up the VM and I was back up and running (I had to resize the partition after I got back into Windows XP but EaseUS Partition Master will take care of that for you without even rebooting and is free).