Backing up your files is one way to keep them safe, but cloning your entire hard drive can be a much more effective solution. The main benefit of doing this is that if something happens and you need to recover your disk, you will also get back all the applications you had installed before, as well as all the customization options you would otherwise lose forever.
Macrium Reflect Free is a tool that lets you clone an entire disk partition, even if you are using it at the same time you want to clone it. You can save the resulting disk image inside the same partition, or on a network, portable drive, or CD/DVD.
The algorithm used by Macrium Reflect Free reduces the size of the disk image drastically, and still achieves an optimum speed. Obviously, you can recover the disk copy right from Macrium Reflect, and even create recovery CDs for Linux.